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 $241.52   9.569%   $264.631   $264.63   $264.65   $264.60  
  Purchase #2 $179.85   12.366%   $202.0903   $202.09   $202.10   $202.10  
  Purchase #3 $157.33   12.426%   $176.8798   $176.88   $176.90   $176.90  
  Purchase #4 $151.84   13.351%   $172.1122   $172.11   $172.10   $172.10  
  Purchase #5 $146.85   4.192%   $153.006   $153.01   $153.00   $153.00  
  Purchase #6 $30.36   12.501%   $34.1553   $34.16   $34.15   $34.20  
  Purchase #7 $65.73   9.703%   $72.1078   $72.11   $72.10   $72.10  
  7 purchase totals = $973.48       $1,074.9824   $1,074.99   $1,075.00   $1,075.00