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 $62.61   11.718%   $69.9466   $69.95   $69.95   $69.90  
  Purchase #2 $182.70   9.575%   $200.1935   $200.19   $200.20   $200.20  
  Purchase #3 $141.90   4.558%   $148.3678   $148.37   $148.35   $148.40  
  Purchase #4 $172.70   8.643%   $187.6265   $187.63   $187.65   $187.60  
  Purchase #5 $139.56   5.537%   $147.2874   $147.29   $147.30   $147.30  
  Purchase #6 $135.53   9.497%   $148.4013   $148.40   $148.40   $148.40  
  Purchase #7 $144.85   5.143%   $152.2996   $152.30   $152.30   $152.30  
  7 purchase totals = $979.85       $1,054.1227   $1,054.13   $1,054.15   $1,054.10