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 $215.71   9.272%   $235.7106   $235.71   $235.70   $235.70  
  Purchase #2 $48.67   12.658%   $54.8306   $54.83   $54.85   $54.80  
  Purchase #3 $194.42   8.410%   $210.7707   $210.77   $210.75   $210.80  
  Purchase #4 $102.58   3.603%   $106.276   $106.28   $106.30   $106.30  
  Purchase #5 $194.90   11.369%   $217.0582   $217.06   $217.05   $217.10  
  Purchase #6 $54.71   6.514%   $58.2738   $58.27   $58.25   $58.30  
  Purchase #7 $205.74   13.448%   $233.4079   $233.41   $233.40   $233.40  
  7 purchase totals = $1,016.73       $1,116.3278   $1,116.33   $1,116.30   $1,116.40