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 $58.86   6.853%   $62.8937   $62.89   $62.90   $62.90  
  Purchase #2 $138.50   9.479%   $151.6284   $151.63   $151.65   $151.60  
  Purchase #3 $210.98   9.690%   $231.424   $231.42   $231.40   $231.40  
  Purchase #4 $212.37   12.398%   $238.6996   $238.70   $238.70   $238.70  
  Purchase #5 $230.81   6.462%   $245.7249   $245.72   $245.70   $245.70  
  Purchase #6 $20.82   11.412%   $23.196   $23.20   $23.20   $23.20  
  Purchase #7 $219.27   11.170%   $243.7625   $243.76   $243.75   $243.80  
  7 purchase totals = $1,091.61       $1,197.3291   $1,197.32   $1,197.30   $1,197.30