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 $31.62   4.781%   $33.1318   $33.13   $33.15   $33.10  
  Purchase #2 $55.90   12.451%   $62.8601   $62.86   $62.85   $62.90  
  Purchase #3 $208.99   3.675%   $216.6704   $216.67   $216.65   $216.70  
  Purchase #4 $65.35   6.611%   $69.6703   $69.67   $69.65   $69.70  
  Purchase #5 $82.64   6.746%   $88.2149   $88.21   $88.20   $88.20  
  Purchase #6 $202.29   11.459%   $225.4704   $225.47   $225.45   $225.50  
  Purchase #7 $58.99   9.592%   $64.6483   $64.65   $64.65   $64.60  
  7 purchase totals = $705.78       $760.6662   $760.66   $760.60   $760.70