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 $53.69   11.408%   $59.815   $59.82   $59.80   $59.80  
  Purchase #2 $126.27   13.187%   $142.9212   $142.92   $142.90   $142.90  
  Purchase #3 $107.94   7.531%   $116.069   $116.07   $116.05   $116.10  
  Purchase #4 $84.59   8.369%   $91.6693   $91.67   $91.65   $91.70  
  Purchase #5 $215.72   6.315%   $229.3427   $229.34   $229.35   $229.30  
  Purchase #6 $220.96   3.303%   $228.2583   $228.26   $228.25   $228.30  
  Purchase #7 $224.64   4.221%   $234.1221   $234.12   $234.10   $234.10  
  7 purchase totals = $1,033.81       $1,102.1976   $1,102.20   $1,102.10   $1,102.20