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 $197.56   7.314%   $212.0095   $212.01   $212.00   $212.00  
  Purchase #2 $187.45   4.457%   $195.8046   $195.80   $195.80   $195.80  
  Purchase #3 $160.51   5.344%   $169.0877   $169.09   $169.10   $169.10  
  Purchase #4 $244.31   7.549%   $262.753   $262.75   $262.75   $262.80  
  Purchase #5 $35.82   8.475%   $38.8557   $38.86   $38.85   $38.90  
  Purchase #6 $181.83   10.646%   $201.1876   $201.19   $201.20   $201.20  
  Purchase #7 $64.45   13.677%   $73.2648   $73.26   $73.25   $73.30  
  7 purchase totals = $1,071.93       $1,152.9629   $1,152.96   $1,152.95   $1,153.10