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 $85.43   11.162%   $94.9657   $94.97   $94.95   $95.00  
  Purchase #2 $56.82   12.478%   $63.91   $63.91   $63.90   $63.90  
  Purchase #3 $192.48   6.696%   $205.3685   $205.37   $205.35   $205.40  
  Purchase #4 $232.60   6.645%   $248.0563   $248.06   $248.05   $248.10  
  Purchase #5 $41.58   6.647%   $44.3438   $44.34   $44.35   $44.30  
  Purchase #6 $209.82   13.713%   $238.5926   $238.59   $238.60   $238.60  
  Purchase #7 $64.46   5.775%   $68.1826   $68.18   $68.20   $68.20  
  7 purchase totals = $883.19       $963.4195   $963.42   $963.40   $963.50