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 $62.92   5.162%   $66.1679   $66.17   $66.15   $66.20  
  Purchase #2 $200.76   5.167%   $211.1333   $211.13   $211.15   $211.10  
  Purchase #3 $157.33   6.479%   $167.5234   $167.52   $167.50   $167.50  
  Purchase #4 $126.87   5.791%   $134.217   $134.22   $134.20   $134.20  
  Purchase #5 $41.71   7.386%   $44.7907   $44.79   $44.80   $44.80  
  Purchase #6 $152.57   9.457%   $166.9985   $167.00   $167.00   $167.00  
  Purchase #7 $220.77   4.767%   $231.2941   $231.29   $231.30   $231.30  
  7 purchase totals = $962.93       $1,022.1249   $1,022.12   $1,022.10   $1,022.10