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 $176.43   3.353%   $182.3457   $182.35   $182.35   $182.30  
  Purchase #2 $161.72   7.161%   $173.3008   $173.30   $173.30   $173.30  
  Purchase #3 $184.97   9.734%   $202.975   $202.98   $203.00   $203.00  
  Purchase #4 $176.37   3.419%   $182.4001   $182.40   $182.40   $182.40  
  Purchase #5 $249.33   5.490%   $263.0182   $263.02   $263.00   $263.00  
  Purchase #6 $62.26   9.767%   $68.3409   $68.34   $68.35   $68.30  
  Purchase #7 $114.30   6.595%   $121.8381   $121.84   $121.85   $121.80  
  7 purchase totals = $1,125.38       $1,194.2188   $1,194.23   $1,194.25   $1,194.10