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 $94.93   11.235%   $105.5954   $105.60   $105.60   $105.60  
  Purchase #2 $240.62   3.603%   $249.2895   $249.29   $249.30   $249.30  
  Purchase #3 $77.49   3.370%   $80.1014   $80.10   $80.10   $80.10  
  Purchase #4 $119.29   6.123%   $126.5941   $126.59   $126.60   $126.60  
  Purchase #5 $153.71   8.208%   $166.3265   $166.33   $166.35   $166.30  
  Purchase #6 $211.60   13.169%   $239.4656   $239.47   $239.45   $239.50  
  Purchase #7 $166.26   11.249%   $184.9626   $184.96   $184.95   $185.00  
  7 purchase totals = $1,063.90       $1,152.3351   $1,152.34   $1,152.35   $1,152.40