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 $118.95   3.461%   $123.0669   $123.07   $123.05   $123.10  
  Purchase #2 $212.71   6.599%   $226.7467   $226.75   $226.75   $226.70  
  Purchase #3 $94.89   10.553%   $104.9037   $104.90   $104.90   $104.90  
  Purchase #4 $244.90   5.169%   $257.5589   $257.56   $257.55   $257.60  
  Purchase #5 $201.39   5.378%   $212.2208   $212.22   $212.20   $212.20  
  Purchase #6 $145.68   4.847%   $152.7411   $152.74   $152.75   $152.70  
  Purchase #7 $140.52   11.400%   $156.5393   $156.54   $156.55   $156.50  
  7 purchase totals = $1,159.04       $1,233.7774   $1,233.78   $1,233.75   $1,233.70