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 $43.46   11.796%   $48.5865   $48.59   $48.60   $48.60  
  Purchase #2 $167.84   13.212%   $190.015   $190.02   $190.00   $190.00  
  Purchase #3 $26.80   4.663%   $28.0497   $28.05   $28.05   $28.00  
  Purchase #4 $203.43   11.523%   $226.8712   $226.87   $226.85   $226.90  
  Purchase #5 $240.61   12.349%   $270.3229   $270.32   $270.30   $270.30  
  Purchase #6 $207.88   3.496%   $215.1475   $215.15   $215.15   $215.10  
  Purchase #7 $181.99   5.475%   $191.954   $191.95   $191.95   $192.00  
  7 purchase totals = $1,072.01       $1,170.9468   $1,170.95   $1,170.90   $1,170.90