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 $114.27   4.361%   $119.2533   $119.25   $119.25   $119.30  
  Purchase #2 $244.95   11.690%   $273.5847   $273.58   $273.60   $273.60  
  Purchase #3 $80.30   5.319%   $84.5712   $84.57   $84.55   $84.60  
  Purchase #4 $187.41   10.166%   $206.4621   $206.46   $206.45   $206.50  
  Purchase #5 $225.39   11.485%   $251.276   $251.28   $251.30   $251.30  
  Purchase #6 $180.98   13.410%   $205.2494   $205.25   $205.25   $205.20  
  Purchase #7 $172.66   3.537%   $178.767   $178.77   $178.75   $178.80  
  7 purchase totals = $1,205.96       $1,319.1637   $1,319.16   $1,319.15   $1,319.30