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 $82.98   11.631%   $92.6314   $92.63   $92.65   $92.60  
  Purchase #2 $181.83   5.483%   $191.7997   $191.80   $191.80   $191.80  
  Purchase #3 $148.62   3.226%   $153.4145   $153.41   $153.40   $153.40  
  Purchase #4 $182.88   12.123%   $205.0505   $205.05   $205.05   $205.10  
  Purchase #5 $201.57   5.765%   $213.1905   $213.19   $213.20   $213.20  
  Purchase #6 $118.46   10.386%   $130.7633   $130.76   $130.75   $130.80  
  Purchase #7 $62.69   9.402%   $68.5841   $68.58   $68.60   $68.60  
  7 purchase totals = $979.03       $1,055.4340   $1,055.42   $1,055.45   $1,055.50