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 $103.38   10.564%   $114.3011   $114.30   $114.30   $114.30  
  Purchase #2 $32.53   4.172%   $33.8872   $33.89   $33.90   $33.90  
  Purchase #3 $127.98   3.700%   $132.7153   $132.72   $132.70   $132.70  
  Purchase #4 $201.94   5.668%   $213.386   $213.39   $213.40   $213.40  
  Purchase #5 $13.83   4.651%   $14.4732   $14.47   $14.45   $14.50  
  Purchase #6 $182.33   11.771%   $203.7921   $203.79   $203.80   $203.80  
  Purchase #7 $42.34   3.140%   $43.6695   $43.67   $43.65   $43.70  
  7 purchase totals = $704.33       $756.2244   $756.23   $756.20   $756.30