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 $199.82   5.462%   $210.7342   $210.73   $210.75   $210.70  
  Purchase #2 $172.27   8.275%   $186.5253   $186.53   $186.55   $186.50  
  Purchase #3 $124.68   3.690%   $129.2807   $129.28   $129.30   $129.30  
  Purchase #4 $88.86   9.155%   $96.9951   $97.00   $97.00   $97.00  
  Purchase #5 $99.86   13.777%   $113.6177   $113.62   $113.60   $113.60  
  Purchase #6 $22.87   9.145%   $24.9615   $24.96   $24.95   $25.00  
  Purchase #7 $218.39   11.427%   $243.3454   $243.35   $243.35   $243.30  
  7 purchase totals = $926.75       $1,005.4599   $1,005.47   $1,005.50   $1,005.40