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 $214.33   5.790%   $226.7397   $226.74   $226.75   $226.70  
  Purchase #2 $178.73   13.600%   $203.0373   $203.04   $203.05   $203.00  
  Purchase #3 $91.48   13.414%   $103.7511   $103.75   $103.75   $103.80  
  Purchase #4 $180.47   5.478%   $190.3561   $190.36   $190.35   $190.40  
  Purchase #5 $127.25   5.721%   $134.53   $134.53   $134.55   $134.50  
  Purchase #6 $205.82   3.232%   $212.4721   $212.47   $212.45   $212.50  
  Purchase #7 $63.72   10.428%   $70.3647   $70.36   $70.35   $70.40  
  7 purchase totals = $1,061.80       $1,141.2510   $1,141.25   $1,141.25   $1,141.30