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	$213.58	11.448%	$238.0306	$238.03	$238.05	$238.00
Purchase #2	$56.31	4.785%	$59.0044	$59.00	$59.00	$59.00
Purchase #3	$112.35	12.482%	$126.3735	$126.37	$126.35	$126.40
Purchase #4	$35.96	6.116%	$38.1593	$38.16	$38.15	$38.20
Purchase #5	$222.88	6.606%	$237.6035	$237.60	$237.60	$237.60
Purchase #6	$160.69	6.269%	$170.7637	$170.76	$170.75	$170.80
Purchase #7	$66.88	6.827%	$71.4459	$71.45	$71.45	$71.40
7 purchase totals =	$868.65		$941.3809	$941.37	$941.35	$941.40