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 $118.57   5.726%   $125.3593   $125.36   $125.35   $125.40  
  Purchase #2 $213.59   13.751%   $242.9608   $242.96   $242.95   $243.00  
  Purchase #3 $176.52   3.446%   $182.6029   $182.60   $182.60   $182.60  
  Purchase #4 $183.58   9.118%   $200.3188   $200.32   $200.30   $200.30  
  Purchase #5 $241.73   13.148%   $273.5127   $273.51   $273.50   $273.50  
  Purchase #6 $113.52   13.506%   $128.852   $128.85   $128.85   $128.90  
  Purchase #7 $20.95   13.401%   $23.7575   $23.76   $23.75   $23.80  
  7 purchase totals = $1,068.46       $1,177.3640   $1,177.36   $1,177.30   $1,177.50