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 $185.68   4.615%   $194.2491   $194.25   $194.25   $194.20  
  Purchase #2 $26.72   11.658%   $29.835   $29.84   $29.85   $29.80  
  Purchase #3 $59.80   13.337%   $67.7755   $67.78   $67.80   $67.80  
  Purchase #4 $210.65   4.127%   $219.3435   $219.34   $219.35   $219.30  
  Purchase #5 $201.85   3.601%   $209.1186   $209.12   $209.10   $209.10  
  Purchase #6 $119.65   11.516%   $133.4289   $133.43   $133.45   $133.40  
  Purchase #7 $233.36   11.262%   $259.641   $259.64   $259.65   $259.60  
  7 purchase totals = $1,037.71       $1,113.3916   $1,113.40   $1,113.45   $1,113.20