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 $96.26   8.840%   $104.7694   $104.77   $104.75   $104.80  
  Purchase #2 $88.59   11.204%   $98.5156   $98.52   $98.50   $98.50  
  Purchase #3 $22.76   12.220%   $25.5413   $25.54   $25.55   $25.50  
  Purchase #4 $112.87   4.305%   $117.7291   $117.73   $117.75   $117.70  
  Purchase #5 $239.84   8.518%   $260.2696   $260.27   $260.25   $260.30  
  Purchase #6 $245.73   10.485%   $271.4948   $271.49   $271.50   $271.50  
  Purchase #7 $147.72   7.808%   $159.254   $159.25   $159.25   $159.30  
  7 purchase totals = $953.77       $1,037.5738   $1,037.57   $1,037.55   $1,037.60