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 $89.46   7.626%   $96.2822   $96.28   $96.30   $96.30  
  Purchase #2 $214.35   7.712%   $230.8807   $230.88   $230.90   $230.90  
  Purchase #3 $204.67   11.598%   $228.4076   $228.41   $228.40   $228.40  
  Purchase #4 $231.36   10.171%   $254.8916   $254.89   $254.90   $254.90  
  Purchase #5 $88.71   4.429%   $92.639   $92.64   $92.65   $92.60  
  Purchase #6 $148.62   12.109%   $166.6164   $166.62   $166.60   $166.60  
  Purchase #7 $44.26   4.338%   $46.18   $46.18   $46.20   $46.20  
  7 purchase totals = $1,021.43       $1,115.8975   $1,115.90   $1,115.95   $1,115.90