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 $61.88   12.479%   $69.602   $69.60   $69.60   $69.60  
  Purchase #2 $183.77   6.208%   $195.1784   $195.18   $195.20   $195.20  
  Purchase #3 $59.79   3.590%   $61.9365   $61.94   $61.95   $61.90  
  Purchase #4 $191.42   10.217%   $210.9774   $210.98   $211.00   $211.00  
  Purchase #5 $210.77   4.598%   $220.4612   $220.46   $220.45   $220.50  
  Purchase #6 $27.61   3.267%   $28.512   $28.51   $28.50   $28.50  
  Purchase #7 $249.49   9.768%   $273.8602   $273.86   $273.85   $273.90  
  7 purchase totals = $984.73       $1,060.5277   $1,060.53   $1,060.55   $1,060.60