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 $208.53   3.632%   $216.1038   $216.10   $216.10   $216.10  
  Purchase #2 $227.34   3.620%   $235.5697   $235.57   $235.55   $235.60  
  Purchase #3 $230.56   3.111%   $237.7327   $237.73   $237.75   $237.70  
  Purchase #4 $56.55   5.814%   $59.8378   $59.84   $59.85   $59.80  
  Purchase #5 $94.63   7.581%   $101.8039   $101.80   $101.80   $101.80  
  Purchase #6 $210.70   4.223%   $219.5979   $219.60   $219.60   $219.60  
  Purchase #7 $164.82   5.425%   $173.7615   $173.76   $173.75   $173.80  
  7 purchase totals = $1,193.13       $1,244.4073   $1,244.40   $1,244.40   $1,244.40