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 $197.49   7.233%   $211.7745   $211.77   $211.75   $211.80  
  Purchase #2 $62.86   13.154%   $71.1286   $71.13   $71.15   $71.10  
  Purchase #3 $151.75   8.245%   $164.2618   $164.26   $164.25   $164.30  
  Purchase #4 $235.90   7.577%   $253.7741   $253.77   $253.75   $253.80  
  Purchase #5 $162.52   6.291%   $172.7441   $172.74   $172.75   $172.70  
  Purchase #6 $168.75   5.408%   $177.876   $177.88   $177.90   $177.90  
  Purchase #7 $148.33   3.310%   $153.2397   $153.24   $153.25   $153.20  
  7 purchase totals = $1,127.60       $1,204.7988   $1,204.79   $1,204.80   $1,204.80