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 $182.46   8.230%   $197.4765   $197.48   $197.50   $197.50  
  Purchase #2 $101.98   5.350%   $107.4359   $107.44   $107.45   $107.40  
  Purchase #3 $83.70   11.237%   $93.1054   $93.11   $93.10   $93.10  
  Purchase #4 $240.58   4.794%   $252.1134   $252.11   $252.10   $252.10  
  Purchase #5 $194.26   3.483%   $201.0261   $201.03   $201.05   $201.00  
  Purchase #6 $155.55   3.107%   $160.3829   $160.38   $160.40   $160.40  
  Purchase #7 $100.93   11.294%   $112.329   $112.33   $112.35   $112.30  
  7 purchase totals = $1,059.46       $1,123.8692   $1,123.88   $1,123.95   $1,123.80