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 $34.85   3.362%   $36.0217   $36.02   $36.00   $36.00  
  Purchase #2 $194.63   10.592%   $215.2452   $215.25   $215.25   $215.20  
  Purchase #3 $41.90   3.831%   $43.5052   $43.51   $43.50   $43.50  
  Purchase #4 $46.65   13.126%   $52.7733   $52.77   $52.75   $52.80  
  Purchase #5 $211.89   4.332%   $221.0691   $221.07   $221.05   $221.10  
  Purchase #6 $157.51   11.871%   $176.208   $176.21   $176.20   $176.20  
  Purchase #7 $220.79   5.144%   $232.1474   $232.15   $232.15   $232.10  
  7 purchase totals = $908.22       $976.9699   $976.98   $976.90   $976.90