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 $67.39   7.338%   $72.3351   $72.34   $72.35   $72.30  
  Purchase #2 $152.71   11.187%   $169.7937   $169.79   $169.80   $169.80  
  Purchase #3 $98.80   11.413%   $110.076   $110.08   $110.10   $110.10  
  Purchase #4 $48.57   12.533%   $54.6573   $54.66   $54.65   $54.70  
  Purchase #5 $192.88   5.776%   $204.0207   $204.02   $204.00   $204.00  
  Purchase #6 $183.43   10.657%   $202.9781   $202.98   $203.00   $203.00  
  Purchase #7 $203.44   10.411%   $224.6201   $224.62   $224.60   $224.60  
  7 purchase totals = $947.22       $1,038.4810   $1,038.49   $1,038.50   $1,038.50