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 $57.68   9.665%   $63.2548   $63.25   $63.25   $63.30  
  Purchase #2 $195.58   4.103%   $203.6046   $203.60   $203.60   $203.60  
  Purchase #3 $178.56   8.854%   $194.3697   $194.37   $194.35   $194.40  
  Purchase #4 $70.50   3.682%   $73.0958   $73.10   $73.10   $73.10  
  Purchase #5 $184.93   8.550%   $200.7415   $200.74   $200.75   $200.70  
  Purchase #6 $200.91   11.313%   $223.6389   $223.64   $223.65   $223.60  
  Purchase #7 $69.83   12.429%   $78.5092   $78.51   $78.50   $78.50  
  7 purchase totals = $957.99       $1,037.2145   $1,037.21   $1,037.20   $1,037.20