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 $184.61   10.505%   $204.0033   $204.00   $204.00   $204.00  
  Purchase #2 $158.59   5.473%   $167.2696   $167.27   $167.25   $167.30  
  Purchase #3 $104.97   5.708%   $110.9617   $110.96   $110.95   $111.00  
  Purchase #4 $125.71   8.641%   $136.5726   $136.57   $136.55   $136.60  
  Purchase #5 $200.98   6.446%   $213.9352   $213.94   $213.95   $213.90  
  Purchase #6 $231.68   8.170%   $250.6083   $250.61   $250.60   $250.60  
  Purchase #7 $11.51   8.550%   $12.4941   $12.49   $12.50   $12.50  
  7 purchase totals = $1,018.05       $1,095.8448   $1,095.84   $1,095.80   $1,095.90