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 $13.94   4.467%   $14.5627   $14.56   $14.55   $14.60  
  Purchase #2 $214.52   10.823%   $237.7375   $237.74   $237.75   $237.70  
  Purchase #3 $179.28   11.821%   $200.4727   $200.47   $200.45   $200.50  
  Purchase #4 $16.51   8.153%   $17.8561   $17.86   $17.85   $17.90  
  Purchase #5 $175.81   9.361%   $192.2676   $192.27   $192.25   $192.30  
  Purchase #6 $44.63   7.808%   $48.1147   $48.11   $48.10   $48.10  
  Purchase #7 $213.75   13.842%   $243.3373   $243.34   $243.35   $243.30  
  7 purchase totals = $858.44       $954.3486   $954.35   $954.30   $954.40