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 $113.64   10.592%   $125.6767   $125.68   $125.70   $125.70  
  Purchase #2 $154.57   5.145%   $162.5226   $162.52   $162.50   $162.50  
  Purchase #3 $8.38   13.656%   $9.5244   $9.52   $9.50   $9.50  
  Purchase #4 $204.75   4.281%   $213.5153   $213.52   $213.50   $213.50  
  Purchase #5 $139.57   13.207%   $158.003   $158.00   $158.00   $158.00  
  Purchase #6 $10.50   9.755%   $11.5243   $11.52   $11.50   $11.50  
  Purchase #7 $134.58   9.430%   $147.2709   $147.27   $147.25   $147.30  
  7 purchase totals = $765.99       $828.0372   $828.03   $827.95   $828.00