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 $192.79   4.658%   $201.7702   $201.77   $201.75   $201.80  
  Purchase #2 $185.88   5.404%   $195.925   $195.93   $195.95   $195.90  
  Purchase #3 $66.50   6.117%   $70.5678   $70.57   $70.55   $70.60  
  Purchase #4 $185.51   7.568%   $199.5494   $199.55   $199.55   $199.50  
  Purchase #5 $125.63   6.278%   $133.5171   $133.52   $133.50   $133.50  
  Purchase #6 $52.86   13.505%   $59.9987   $60.00   $60.00   $60.00  
  Purchase #7 $175.77   11.124%   $195.3227   $195.32   $195.30   $195.30  
  7 purchase totals = $984.94       $1,056.6509   $1,056.66   $1,056.60   $1,056.60