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 $216.55   3.563%   $224.2657   $224.27   $224.25   $224.30  
  Purchase #2 $200.74   8.113%   $217.026   $217.03   $217.05   $217.00  
  Purchase #3 $162.99   4.700%   $170.6505   $170.65   $170.65   $170.70  
  Purchase #4 $202.90   11.793%   $226.828   $226.83   $226.85   $226.80  
  Purchase #5 $162.91   10.442%   $179.9211   $179.92   $179.90   $179.90  
  Purchase #6 $103.46   11.740%   $115.6062   $115.61   $115.60   $115.60  
  Purchase #7 $218.25   9.530%   $239.0492   $239.05   $239.05   $239.00  
  7 purchase totals = $1,267.80       $1,373.3467   $1,373.36   $1,373.35   $1,373.30