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 $190.57   5.481%   $201.0151   $201.02   $201.00   $201.00  
  Purchase #2 $13.34   7.508%   $14.3416   $14.34   $14.35   $14.30  
  Purchase #3 $170.36   12.568%   $191.7708   $191.77   $191.75   $191.80  
  Purchase #4 $106.33   9.415%   $116.341   $116.34   $116.35   $116.30  
  Purchase #5 $222.86   8.414%   $241.6114   $241.61   $241.60   $241.60  
  Purchase #6 $12.93   5.450%   $13.6347   $13.63   $13.65   $13.60  
  Purchase #7 $174.26   5.485%   $183.8182   $183.82   $183.80   $183.80  
  7 purchase totals = $890.65       $962.5328   $962.53   $962.50   $962.40