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 $211.38   10.712%   $234.023   $234.02   $234.00   $234.00  
  Purchase #2 $204.55   12.746%   $230.6219   $230.62   $230.60   $230.60  
  Purchase #3 $172.45   11.193%   $191.7523   $191.75   $191.75   $191.80  
  Purchase #4 $187.71   3.559%   $194.3906   $194.39   $194.40   $194.40  
  Purchase #5 $197.28   6.731%   $210.5589   $210.56   $210.55   $210.60  
  Purchase #6 $86.34   7.366%   $92.6998   $92.70   $92.70   $92.70  
  Purchase #7 $191.41   6.668%   $204.1732   $204.17   $204.15   $204.20  
  7 purchase totals = $1,251.12       $1,358.2197   $1,358.21   $1,358.15   $1,358.30