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 $182.65   7.472%   $196.2976   $196.30   $196.30   $196.30  
  Purchase #2 $239.72   11.805%   $268.0189   $268.02   $268.00   $268.00  
  Purchase #3 $233.50   8.291%   $252.8595   $252.86   $252.85   $252.90  
  Purchase #4 $217.29   13.273%   $246.1309   $246.13   $246.15   $246.10  
  Purchase #5 $60.86   3.407%   $62.9335   $62.93   $62.95   $62.90  
  Purchase #6 $119.59   10.336%   $131.9508   $131.95   $131.95   $132.00  
  Purchase #7 $138.45   5.175%   $145.6148   $145.61   $145.60   $145.60  
  7 purchase totals = $1,192.06       $1,303.8060   $1,303.80   $1,303.80   $1,303.80