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 $172.53   13.218%   $195.335   $195.34   $195.35   $195.30  
  Purchase #2 $234.69   4.709%   $245.7416   $245.74   $245.75   $245.70  
  Purchase #3 $166.84   9.445%   $182.598   $182.60   $182.60   $182.60  
  Purchase #4 $206.78   5.673%   $218.5106   $218.51   $218.50   $218.50  
  Purchase #5 $228.67   3.106%   $235.7725   $235.77   $235.75   $235.80  
  Purchase #6 $98.79   7.835%   $106.5302   $106.53   $106.55   $106.50  
  Purchase #7 $182.27   5.609%   $192.4935   $192.49   $192.50   $192.50  
  7 purchase totals = $1,290.57       $1,376.9814   $1,376.98   $1,377.00   $1,376.90