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 $212.71   7.283%   $228.2017   $228.20   $228.20   $228.20  
  Purchase #2 $127.60   4.714%   $133.6151   $133.62   $133.60   $133.60  
  Purchase #3 $206.43   6.853%   $220.5766   $220.58   $220.60   $220.60  
  Purchase #4 $59.83   4.503%   $62.5241   $62.52   $62.50   $62.50  
  Purchase #5 $221.26   11.782%   $247.3289   $247.33   $247.35   $247.30  
  Purchase #6 $190.49   3.792%   $197.7134   $197.71   $197.70   $197.70  
  Purchase #7 $243.79   9.391%   $266.6843   $266.68   $266.70   $266.70  
  7 purchase totals = $1,262.11       $1,356.6441   $1,356.64   $1,356.65   $1,356.60