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 $44.68   7.331%   $47.9555   $47.96   $47.95   $48.00  
  Purchase #2 $153.70   12.623%   $173.1016   $173.10   $173.10   $173.10  
  Purchase #3 $177.37   5.228%   $186.6429   $186.64   $186.65   $186.60  
  Purchase #4 $95.48   5.264%   $100.5061   $100.51   $100.50   $100.50  
  Purchase #5 $152.53   3.744%   $158.2407   $158.24   $158.25   $158.20  
  Purchase #6 $163.60   5.489%   $172.58   $172.58   $172.60   $172.60  
  Purchase #7 $209.53   11.284%   $233.1734   $233.17   $233.15   $233.20  
  7 purchase totals = $996.89       $1,072.2002   $1,072.20   $1,072.20   $1,072.20