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 $84.74   13.606%   $96.2697   $96.27   $96.25   $96.30  
  Purchase #2 $219.40   7.603%   $236.081   $236.08   $236.10   $236.10  
  Purchase #3 $61.73   7.262%   $66.2128   $66.21   $66.20   $66.20  
  Purchase #4 $235.81   11.551%   $263.0484   $263.05   $263.05   $263.00  
  Purchase #5 $61.27   7.303%   $65.7445   $65.74   $65.75   $65.70  
  Purchase #6 $153.97   11.297%   $171.364   $171.36   $171.35   $171.40  
  Purchase #7 $62.48   9.355%   $68.325   $68.33   $68.35   $68.30  
  7 purchase totals = $879.40       $967.0454   $967.04   $967.05   $967.00