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 $162.35   8.433%   $176.041   $176.04   $176.05   $176.00  
  Purchase #2 $191.87   10.129%   $211.3045   $211.30   $211.30   $211.30  
  Purchase #3 $74.62   13.626%   $84.7877   $84.79   $84.80   $84.80  
  Purchase #4 $202.75   11.117%   $225.2897   $225.29   $225.30   $225.30  
  Purchase #5 $205.32   11.494%   $228.9195   $228.92   $228.90   $228.90  
  Purchase #6 $116.95   7.630%   $125.8733   $125.87   $125.85   $125.90  
  Purchase #7 $148.43   6.145%   $157.551   $157.55   $157.55   $157.60  
  7 purchase totals = $1,102.29       $1,209.7667   $1,209.76   $1,209.75   $1,209.80