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 $62.56   7.460%   $67.227   $67.23   $67.25   $67.20  
  Purchase #2 $52.60   12.133%   $58.982   $58.98   $59.00   $59.00  
  Purchase #3 $75.73   4.409%   $79.0689   $79.07   $79.05   $79.10  
  Purchase #4 $14.38   3.187%   $14.8383   $14.84   $14.85   $14.80  
  Purchase #5 $203.52   3.328%   $210.2931   $210.29   $210.30   $210.30  
  Purchase #6 $176.45   5.581%   $186.2977   $186.30   $186.30   $186.30  
  Purchase #7 $172.37   8.324%   $186.7181   $186.72   $186.70   $186.70  
  7 purchase totals = $757.61       $803.4251   $803.43   $803.45   $803.40