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 $62.47   11.553%   $69.6872   $69.69   $69.70   $69.70  
  Purchase #2 $135.84   5.740%   $143.6372   $143.64   $143.65   $143.60  
  Purchase #3 $45.79   3.567%   $47.4233   $47.42   $47.40   $47.40  
  Purchase #4 $241.30   6.466%   $256.9025   $256.90   $256.90   $256.90  
  Purchase #5 $177.33   6.700%   $189.2111   $189.21   $189.20   $189.20  
  Purchase #6 $241.98   7.657%   $260.5084   $260.51   $260.50   $260.50  
  Purchase #7 $70.32   7.848%   $75.8387   $75.84   $75.85   $75.80  
  7 purchase totals = $975.03       $1,043.2084   $1,043.21   $1,043.20   $1,043.10