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 $175.67   11.150%   $195.2572   $195.26   $195.25   $195.30  
  Purchase #2 $247.92   7.501%   $266.5165   $266.52   $266.50   $266.50  
  Purchase #3 $60.76   3.856%   $63.1029   $63.10   $63.10   $63.10  
  Purchase #4 $127.70   3.857%   $132.6254   $132.63   $132.65   $132.60  
  Purchase #5 $178.26   9.869%   $195.8525   $195.85   $195.85   $195.90  
  Purchase #6 $230.33   4.326%   $240.2941   $240.29   $240.30   $240.30  
  Purchase #7 $59.31   7.495%   $63.7553   $63.76   $63.75   $63.80  
  7 purchase totals = $1,079.95       $1,157.4039   $1,157.41   $1,157.40   $1,157.50