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 $95.75   5.813%   $101.3159   $101.32   $101.30   $101.30  
  Purchase #2 $55.52   8.240%   $60.0948   $60.09   $60.10   $60.10  
  Purchase #3 $77.35   12.486%   $87.0079   $87.01   $87.00   $87.00  
  Purchase #4 $88.50   5.464%   $93.3356   $93.34   $93.35   $93.30  
  Purchase #5 $155.84   8.723%   $169.4339   $169.43   $169.45   $169.40  
  Purchase #6 $247.35   5.305%   $260.4719   $260.47   $260.45   $260.50  
  Purchase #7 $85.81   11.851%   $95.9793   $95.98   $96.00   $96.00  
  7 purchase totals = $806.12       $867.6393   $867.64   $867.65   $867.60