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 $243.65   9.607%   $267.0575   $267.06   $267.05   $267.10  
  Purchase #2 $162.69   4.516%   $170.0371   $170.04   $170.05   $170.00  
  Purchase #3 $250.66   7.503%   $269.467   $269.47   $269.45   $269.50  
  Purchase #4 $156.49   11.828%   $174.9996   $175.00   $175.00   $175.00  
  Purchase #5 $203.34   9.592%   $222.8444   $222.84   $222.85   $222.80  
  Purchase #6 $233.98   5.851%   $247.6702   $247.67   $247.65   $247.70  
  Purchase #7 $116.45   12.254%   $130.7198   $130.72   $130.70   $130.70  
  7 purchase totals = $1,367.26       $1,482.7956   $1,482.80   $1,482.75   $1,482.80