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 $217.56   13.702%   $247.3701   $247.37   $247.35   $247.40  
  Purchase #2 $87.36   7.664%   $94.0553   $94.06   $94.05   $94.10  
  Purchase #3 $86.76   6.775%   $92.638   $92.64   $92.65   $92.60  
  Purchase #4 $236.80   3.262%   $244.5244   $244.52   $244.50   $244.50  
  Purchase #5 $121.77   3.137%   $125.5899   $125.59   $125.60   $125.60  
  Purchase #6 $205.34   6.795%   $219.2929   $219.29   $219.30   $219.30  
  Purchase #7 $65.54   11.458%   $73.0496   $73.05   $73.05   $73.00  
  7 purchase totals = $1,021.13       $1,096.5202   $1,096.52   $1,096.50   $1,096.50