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 $59.35   5.372%   $62.5383   $62.54   $62.55   $62.50  
  Purchase #2 $148.66   3.556%   $153.9463   $153.95   $153.95   $153.90  
  Purchase #3 $121.48   9.396%   $132.8943   $132.89   $132.90   $132.90  
  Purchase #4 $10.43   7.809%   $11.2445   $11.24   $11.25   $11.20  
  Purchase #5 $240.65   6.554%   $256.4222   $256.42   $256.40   $256.40  
  Purchase #6 $238.31   5.577%   $251.6005   $251.60   $251.60   $251.60  
  Purchase #7 $112.98   11.612%   $126.0992   $126.10   $126.10   $126.10  
  7 purchase totals = $931.86       $994.7453   $994.74   $994.75   $994.60