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 $53.76   13.819%   $61.1891   $61.19   $61.20   $61.20  
  Purchase #2 $89.86   8.471%   $97.472   $97.47   $97.45   $97.50  
  Purchase #3 $11.92   4.462%   $12.4519   $12.45   $12.45   $12.50  
  Purchase #4 $247.65   8.460%   $268.6012   $268.60   $268.60   $268.60  
  Purchase #5 $213.56   11.148%   $237.3677   $237.37   $237.35   $237.40  
  Purchase #6 $230.43   11.186%   $256.2059   $256.21   $256.20   $256.20  
  Purchase #7 $190.43   12.391%   $214.0262   $214.03   $214.05   $214.00  
  7 purchase totals = $1,037.61       $1,147.3140   $1,147.32   $1,147.30   $1,147.40