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 $32.77   6.711%   $34.9692   $34.97   $34.95   $35.00  
  Purchase #2 $152.89   9.723%   $167.7555   $167.76   $167.75   $167.80  
  Purchase #3 $230.35   6.637%   $245.6383   $245.64   $245.65   $245.60  
  Purchase #4 $196.65   13.249%   $222.7042   $222.70   $222.70   $222.70  
  Purchase #5 $162.46   8.596%   $176.4251   $176.43   $176.45   $176.40  
  Purchase #6 $224.61   7.448%   $241.339   $241.34   $241.35   $241.30  
  Purchase #7 $104.36   13.405%   $118.3495   $118.35   $118.35   $118.30  
  7 purchase totals = $1,104.09       $1,207.1808   $1,207.19   $1,207.20   $1,207.10