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 $161.60   3.539%   $167.319   $167.32   $167.30   $167.30  
  Purchase #2 $45.31   5.471%   $47.7889   $47.79   $47.80   $47.80  
  Purchase #3 $195.28   6.834%   $208.6254   $208.63   $208.65   $208.60  
  Purchase #4 $227.92   10.210%   $251.1906   $251.19   $251.20   $251.20  
  Purchase #5 $16.76   6.223%   $17.803   $17.80   $17.80   $17.80  
  Purchase #6 $220.74   10.537%   $243.9994   $244.00   $244.00   $244.00  
  Purchase #7 $195.71   5.478%   $206.431   $206.43   $206.45   $206.40  
  7 purchase totals = $1,063.32       $1,143.1573   $1,143.16   $1,143.20   $1,143.10