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 $85.43   12.354%   $95.984   $95.98   $96.00   $96.00  
  Purchase #2 $166.75   10.212%   $183.7785   $183.78   $183.80   $183.80  
  Purchase #3 $28.35   10.269%   $31.2613   $31.26   $31.25   $31.30  
  Purchase #4 $245.89   4.364%   $256.6206   $256.62   $256.60   $256.60  
  Purchase #5 $197.74   4.370%   $206.3812   $206.38   $206.40   $206.40  
  Purchase #6 $209.55   7.319%   $224.887   $224.89   $224.90   $224.90  
  Purchase #7 $10.29   4.315%   $10.734   $10.73   $10.75   $10.70  
  7 purchase totals = $944.00       $1,009.6466   $1,009.64   $1,009.70   $1,009.70