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 $94.37   4.874%   $98.9696   $98.97   $98.95   $99.00  
  Purchase #2 $91.85   13.549%   $104.2948   $104.29   $104.30   $104.30  
  Purchase #3 $60.74   4.456%   $63.4466   $63.45   $63.45   $63.40  
  Purchase #4 $226.59   3.142%   $233.7095   $233.71   $233.70   $233.70  
  Purchase #5 $72.72   11.723%   $81.245   $81.25   $81.25   $81.20  
  Purchase #6 $213.54   6.390%   $227.1852   $227.19   $227.20   $227.20  
  Purchase #7 $229.78   6.613%   $244.9754   $244.98   $245.00   $245.00  
  7 purchase totals = $989.59       $1,053.8261   $1,053.84   $1,053.85   $1,053.80