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 $214.85   13.102%   $242.9996   $243.00   $243.00   $243.00  
  Purchase #2 $153.54   12.872%   $173.3037   $173.30   $173.30   $173.30  
  Purchase #3 $152.71   13.770%   $173.7382   $173.74   $173.75   $173.70  
  Purchase #4 $168.34   9.803%   $184.8424   $184.84   $184.85   $184.80  
  Purchase #5 $24.94   3.410%   $25.7905   $25.79   $25.80   $25.80  
  Purchase #6 $124.69   10.572%   $137.8722   $137.87   $137.85   $137.90  
  Purchase #7 $67.90   11.123%   $75.4525   $75.45   $75.45   $75.50  
  7 purchase totals = $906.97       $1,013.9991   $1,013.99   $1,014.00   $1,014.00