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 $209.73   11.305%   $233.44   $233.44   $233.45   $233.40  
  Purchase #2 $136.27   10.312%   $150.3222   $150.32   $150.30   $150.30  
  Purchase #3 $68.78   7.553%   $73.975   $73.98   $74.00   $74.00  
  Purchase #4 $47.81   13.355%   $54.195   $54.20   $54.20   $54.20  
  Purchase #5 $131.31   3.193%   $135.5027   $135.50   $135.50   $135.50  
  Purchase #6 $172.40   12.825%   $194.5103   $194.51   $194.50   $194.50  
  Purchase #7 $167.99   9.606%   $184.1271   $184.13   $184.15   $184.10  
  7 purchase totals = $934.29       $1,026.0723   $1,026.08   $1,026.10   $1,026.00