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 $60.43   4.175%   $62.953   $62.95   $62.95   $63.00  
  Purchase #2 $124.61   12.835%   $140.6037   $140.60   $140.60   $140.60  
  Purchase #3 $91.30   8.235%   $98.8186   $98.82   $98.80   $98.80  
  Purchase #4 $101.53   10.872%   $112.5683   $112.57   $112.55   $112.60  
  Purchase #5 $87.27   9.751%   $95.7797   $95.78   $95.80   $95.80  
  Purchase #6 $180.80   11.697%   $201.9482   $201.95   $201.95   $201.90  
  Purchase #7 $139.84   3.463%   $144.6827   $144.68   $144.70   $144.70  
  7 purchase totals = $785.78       $857.3542   $857.35   $857.35   $857.40