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 $67.36   7.539%   $72.4383   $72.44   $72.45   $72.40  
  Purchase #2 $230.51   13.800%   $262.3204   $262.32   $262.30   $262.30  
  Purchase #3 $104.92   5.448%   $110.636   $110.64   $110.65   $110.60  
  Purchase #4 $179.31   7.601%   $192.9394   $192.94   $192.95   $192.90  
  Purchase #5 $147.40   10.190%   $162.4201   $162.42   $162.40   $162.40  
  Purchase #6 $226.79   8.487%   $246.0377   $246.04   $246.05   $246.00  
  Purchase #7 $89.53   13.451%   $101.5727   $101.57   $101.55   $101.60  
  7 purchase totals = $1,045.82       $1,148.3646   $1,148.37   $1,148.35   $1,148.20