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 $182.28   6.822%   $194.7151   $194.72   $194.70   $194.70  
  Purchase #2 $209.91   10.190%   $231.2998   $231.30   $231.30   $231.30  
  Purchase #3 $208.47   3.864%   $216.5253   $216.53   $216.55   $216.50  
  Purchase #4 $44.29   8.464%   $48.0387   $48.04   $48.05   $48.00  
  Purchase #5 $85.25   3.702%   $88.406   $88.41   $88.40   $88.40  
  Purchase #6 $147.54   8.641%   $160.2889   $160.29   $160.30   $160.30  
  Purchase #7 $205.88   9.369%   $225.1689   $225.17   $225.15   $225.20  
  7 purchase totals = $1,083.62       $1,164.4427   $1,164.46   $1,164.45   $1,164.40