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 $85.28   13.713%   $96.9744   $96.97   $96.95   $97.00  
  Purchase #2 $188.96   8.141%   $204.3432   $204.34   $204.35   $204.30  
  Purchase #3 $41.54   10.789%   $46.0218   $46.02   $46.00   $46.00  
  Purchase #4 $7.53   9.118%   $8.2166   $8.22   $8.20   $8.20  
  Purchase #5 $205.43   3.819%   $213.2754   $213.28   $213.30   $213.30  
  Purchase #6 $60.79   8.402%   $65.8976   $65.90   $65.90   $65.90  
  Purchase #7 $59.98   3.659%   $62.1747   $62.17   $62.15   $62.20  
  7 purchase totals = $649.51       $696.9037   $696.90   $696.85   $696.90