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 $136.34   10.765%   $151.017   $151.02   $151.00   $151.00  
  Purchase #2 $96.29   12.400%   $108.23   $108.23   $108.25   $108.20  
  Purchase #3 $165.47   10.603%   $183.0148   $183.01   $183.00   $183.00  
  Purchase #4 $203.89   5.240%   $214.5738   $214.57   $214.55   $214.60  
  Purchase #5 $181.63   3.523%   $188.0288   $188.03   $188.05   $188.00  
  Purchase #6 $160.60   3.594%   $166.372   $166.37   $166.35   $166.40  
  Purchase #7 $57.75   10.872%   $64.0286   $64.03   $64.05   $64.00  
  7 purchase totals = $1,001.97       $1,075.2650   $1,075.26   $1,075.25   $1,075.20