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 $111.85   12.348%   $125.6612   $125.66   $125.65   $125.70  
  Purchase #2 $172.54   5.403%   $181.8623   $181.86   $181.85   $181.90  
  Purchase #3 $201.45   3.772%   $209.0487   $209.05   $209.05   $209.00  
  Purchase #4 $150.99   7.278%   $161.9791   $161.98   $162.00   $162.00  
  Purchase #5 $187.71   12.234%   $210.6744   $210.67   $210.65   $210.70  
  Purchase #6 $194.48   5.352%   $204.8886   $204.89   $204.90   $204.90  
  Purchase #7 $67.42   8.428%   $73.1022   $73.10   $73.10   $73.10  
  7 purchase totals = $1,086.44       $1,167.2165   $1,167.21   $1,167.20   $1,167.30