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 $43.56   9.489%   $47.6934   $47.69   $47.70   $47.70  
  Purchase #2 $205.85   6.807%   $219.8622   $219.86   $219.85   $219.90  
  Purchase #3 $36.87   6.344%   $39.209   $39.21   $39.20   $39.20  
  Purchase #4 $228.34   12.196%   $256.1883   $256.19   $256.20   $256.20  
  Purchase #5 $44.95   8.525%   $48.782   $48.78   $48.80   $48.80  
  Purchase #6 $237.35   12.618%   $267.2988   $267.30   $267.30   $267.30  
  Purchase #7 $138.60   3.859%   $143.9486   $143.95   $143.95   $143.90  
  7 purchase totals = $935.52       $1,022.9823   $1,022.98   $1,023.00   $1,023.00