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 $92.70   3.644%   $96.078   $96.08   $96.10   $96.10  
  Purchase #2 $206.66   9.199%   $225.6707   $225.67   $225.65   $225.70  
  Purchase #3 $233.69   13.132%   $264.3782   $264.38   $264.40   $264.40  
  Purchase #4 $180.37   9.530%   $197.5593   $197.56   $197.55   $197.60  
  Purchase #5 $188.94   13.177%   $213.8366   $213.84   $213.85   $213.80  
  Purchase #6 $234.75   7.591%   $252.5699   $252.57   $252.55   $252.60  
  Purchase #7 $221.41   9.263%   $241.9192   $241.92   $241.90   $241.90  
  7 purchase totals = $1,358.52       $1,492.0119   $1,492.02   $1,492.00   $1,492.10