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 $69.95   7.529%   $75.2165   $75.22   $75.20   $75.20  
  Purchase #2 $198.53   3.240%   $204.9624   $204.96   $204.95   $205.00  
  Purchase #3 $198.42   3.138%   $204.6464   $204.65   $204.65   $204.60  
  Purchase #4 $70.55   3.151%   $72.773   $72.77   $72.75   $72.80  
  Purchase #5 $147.64   5.130%   $155.2139   $155.21   $155.20   $155.20  
  Purchase #6 $25.75   13.816%   $29.3076   $29.31   $29.30   $29.30  
  Purchase #7 $182.97   10.637%   $202.4325   $202.43   $202.45   $202.40  
  7 purchase totals = $893.81       $944.5523   $944.55   $944.50   $944.50