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 $207.60   5.481%   $218.9786   $218.98   $219.00   $219.00  
  Purchase #2 $23.34   10.751%   $25.8493   $25.85   $25.85   $25.80  
  Purchase #3 $28.43   6.465%   $30.268   $30.27   $30.25   $30.30  
  Purchase #4 $189.99   9.578%   $208.1872   $208.19   $208.20   $208.20  
  Purchase #5 $99.47   10.603%   $110.0168   $110.02   $110.00   $110.00  
  Purchase #6 $205.80   8.694%   $223.6923   $223.69   $223.70   $223.70  
  Purchase #7 $187.67   5.361%   $197.731   $197.73   $197.75   $197.70  
  7 purchase totals = $942.30       $1,014.7232   $1,014.73   $1,014.75   $1,014.70