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 $244.50   9.416%   $267.5221   $267.52   $267.50   $267.50  
  Purchase #2 $58.84   13.197%   $66.6051   $66.61   $66.60   $66.60  
  Purchase #3 $234.51   10.362%   $258.8099   $258.81   $258.80   $258.80  
  Purchase #4 $45.84   6.742%   $48.9305   $48.93   $48.95   $48.90  
  Purchase #5 $88.70   7.559%   $95.4048   $95.40   $95.40   $95.40  
  Purchase #6 $129.32   3.379%   $133.6897   $133.69   $133.70   $133.70  
  Purchase #7 $232.53   11.449%   $259.1524   $259.15   $259.15   $259.20  
  7 purchase totals = $1,034.24       $1,130.1145   $1,130.11   $1,130.10   $1,130.10