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 $203.36   13.868%   $231.562   $231.56   $231.55   $231.60  
  Purchase #2 $24.33   4.172%   $25.345   $25.35   $25.35   $25.30  
  Purchase #3 $185.39   9.289%   $202.6109   $202.61   $202.60   $202.60  
  Purchase #4 $240.75   9.581%   $263.8163   $263.82   $263.80   $263.80  
  Purchase #5 $142.80   9.272%   $156.0404   $156.04   $156.05   $156.00  
  Purchase #6 $216.60   9.306%   $236.7568   $236.76   $236.75   $236.80  
  Purchase #7 $80.29   9.694%   $88.0733   $88.07   $88.05   $88.10  
  7 purchase totals = $1,093.52       $1,204.2047   $1,204.21   $1,204.15   $1,204.20