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 $61.46   13.842%   $69.9673   $69.97   $69.95   $70.00  
  Purchase #2 $62.59   11.611%   $69.8573   $69.86   $69.85   $69.90  
  Purchase #3 $60.63   12.613%   $68.2773   $68.28   $68.30   $68.30  
  Purchase #4 $12.52   6.456%   $13.3283   $13.33   $13.35   $13.30  
  Purchase #5 $212.54   11.614%   $237.2244   $237.22   $237.20   $237.20  
  Purchase #6 $174.49   11.165%   $193.9718   $193.97   $193.95   $194.00  
  Purchase #7 $42.33   8.791%   $46.0512   $46.05   $46.05   $46.10  
  7 purchase totals = $626.56       $698.6776   $698.68   $698.65   $698.80