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 $84.93   11.860%   $95.0027   $95.00   $95.00   $95.00  
  Purchase #2 $156.60   10.759%   $173.4486   $173.45   $173.45   $173.40  
  Purchase #3 $236.88   4.320%   $247.1132   $247.11   $247.10   $247.10  
  Purchase #4 $99.65   12.765%   $112.3703   $112.37   $112.35   $112.40  
  Purchase #5 $238.30   9.305%   $260.4738   $260.47   $260.45   $260.50  
  Purchase #6 $96.95   8.286%   $104.9833   $104.98   $105.00   $105.00  
  Purchase #7 $242.98   6.736%   $259.3471   $259.35   $259.35   $259.30  
  7 purchase totals = $1,156.29       $1,252.7390   $1,252.73   $1,252.70   $1,252.70