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 $184.54   5.410%   $194.5236   $194.52   $194.50   $194.50  
  Purchase #2 $25.62   7.868%   $27.6358   $27.64   $27.65   $27.60  
  Purchase #3 $95.26   5.333%   $100.3402   $100.34   $100.35   $100.30  
  Purchase #4 $183.53   12.501%   $206.4731   $206.47   $206.45   $206.50  
  Purchase #5 $248.54   9.722%   $272.7031   $272.70   $272.70   $272.70  
  Purchase #6 $219.54   13.647%   $249.5006   $249.50   $249.50   $249.50  
  Purchase #7 $148.78   4.293%   $155.1671   $155.17   $155.15   $155.20  
  7 purchase totals = $1,105.81       $1,206.3435   $1,206.34   $1,206.30   $1,206.30