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 $246.28   3.527%   $254.9663   $254.97   $254.95   $255.00  
  Purchase #2 $101.96   9.846%   $111.999   $112.00   $112.00   $112.00  
  Purchase #3 $42.98   3.853%   $44.636   $44.64   $44.65   $44.60  
  Purchase #4 $165.74   6.265%   $176.1236   $176.12   $176.10   $176.10  
  Purchase #5 $203.65   6.381%   $216.6449   $216.64   $216.65   $216.60  
  Purchase #6 $165.81   6.731%   $176.9707   $176.97   $176.95   $177.00  
  Purchase #7 $167.63   8.430%   $181.7612   $181.76   $181.75   $181.80  
  7 purchase totals = $1,094.05       $1,163.1017   $1,163.10   $1,163.05   $1,163.10