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 $68.83   6.344%   $73.1966   $73.20   $73.20   $73.20  
  Purchase #2 $218.69   11.725%   $244.3314   $244.33   $244.35   $244.30  
  Purchase #3 $86.64   11.541%   $96.6391   $96.64   $96.65   $96.60  
  Purchase #4 $88.50   7.245%   $94.9118   $94.91   $94.90   $94.90  
  Purchase #5 $237.78   11.658%   $265.5004   $265.50   $265.50   $265.50  
  Purchase #6 $245.84   11.689%   $274.5762   $274.58   $274.60   $274.60  
  Purchase #7 $127.59   6.561%   $135.9612   $135.96   $135.95   $136.00  
  7 purchase totals = $1,073.87       $1,185.1167   $1,185.12   $1,185.15   $1,185.10