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 $64.79   10.661%   $71.6973   $71.70   $71.70   $71.70  
  Purchase #2 $201.93   11.465%   $225.0813   $225.08   $225.10   $225.10  
  Purchase #3 $216.76   7.667%   $233.379   $233.38   $233.40   $233.40  
  Purchase #4 $219.74   3.672%   $227.8089   $227.81   $227.80   $227.80  
  Purchase #5 $192.70   12.671%   $217.117   $217.12   $217.10   $217.10  
  Purchase #6 $224.90   9.872%   $247.1021   $247.10   $247.10   $247.10  
  Purchase #7 $38.91   6.784%   $41.5497   $41.55   $41.55   $41.50  
  7 purchase totals = $1,159.73       $1,263.7353   $1,263.74   $1,263.75   $1,263.70