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 $62.84   10.514%   $69.447   $69.45   $69.45   $69.40  
  Purchase #2 $61.40   12.166%   $68.8699   $68.87   $68.85   $68.90  
  Purchase #3 $106.73   12.477%   $120.0467   $120.05   $120.05   $120.00  
  Purchase #4 $239.96   13.690%   $272.8105   $272.81   $272.80   $272.80  
  Purchase #5 $236.77   7.674%   $254.9397   $254.94   $254.95   $254.90  
  Purchase #6 $214.45   4.123%   $223.2918   $223.29   $223.30   $223.30  
  Purchase #7 $171.80   13.802%   $195.5118   $195.51   $195.50   $195.50  
  7 purchase totals = $1,093.95       $1,204.9174   $1,204.92   $1,204.90   $1,204.80