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 $216.98   8.173%   $234.7138   $234.71   $234.70   $234.70  
  Purchase #2 $108.37   9.537%   $118.7052   $118.71   $118.70   $118.70  
  Purchase #3 $194.94   5.734%   $206.1179   $206.12   $206.10   $206.10  
  Purchase #4 $61.45   6.710%   $65.5733   $65.57   $65.55   $65.60  
  Purchase #5 $150.75   13.513%   $171.1208   $171.12   $171.10   $171.10  
  Purchase #6 $195.35   10.551%   $215.9614   $215.96   $215.95   $216.00  
  Purchase #7 $89.91   6.710%   $95.943   $95.94   $95.95   $95.90  
  7 purchase totals = $1,017.75       $1,108.1354   $1,108.13   $1,108.05   $1,108.10