Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $182.61   6.633%   $194.7225   $194.72   $194.70   $194.70  
  Purchase #2 $208.88   13.155%   $236.3582   $236.36   $236.35   $236.40  
  Purchase #3 $107.50   12.390%   $120.8193   $120.82   $120.80   $120.80  
  Purchase #4 $170.81   3.175%   $176.2332   $176.23   $176.25   $176.20  
  Purchase #5 $142.47   12.314%   $160.0138   $160.01   $160.00   $160.00  
  Purchase #6 $113.36   11.217%   $126.0756   $126.08   $126.10   $126.10  
  Purchase #7 $169.37   9.299%   $185.1197   $185.12   $185.10   $185.10  
  7 purchase totals = $1,095.00       $1,199.3423   $1,199.34   $1,199.30   $1,199.30