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 $88.74   8.607%   $96.3779   $96.38   $96.40   $96.40  
  Purchase #2 $229.72   7.329%   $246.5562   $246.56   $246.55   $246.60  
  Purchase #3 $220.64   11.675%   $246.3997   $246.40   $246.40   $246.40  
  Purchase #4 $118.96   11.665%   $132.8367   $132.84   $132.85   $132.80  
  Purchase #5 $133.34   7.115%   $142.8271   $142.83   $142.85   $142.80  
  Purchase #6 $104.74   8.794%   $113.9508   $113.95   $113.95   $114.00  
  Purchase #7 $220.68   6.546%   $235.1257   $235.13   $235.15   $235.10  
  7 purchase totals = $1,116.82       $1,214.0741   $1,214.09   $1,214.15   $1,214.10