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	$238.79	11.636%	$266.5756	$266.58	$266.60	$266.60
Purchase #2	$65.51	3.319%	$67.6843	$67.68	$67.70	$67.70
Purchase #3	$63.69	12.454%	$71.622	$71.62	$71.60	$71.60
Purchase #4	$225.56	12.859%	$254.5648	$254.56	$254.55	$254.60
Purchase #5	$211.78	12.848%	$238.9895	$238.99	$239.00	$239.00
Purchase #6	$243.75	3.112%	$251.3355	$251.34	$251.35	$251.30
Purchase #7	$106.95	4.294%	$111.5424	$111.54	$111.55	$111.50
7 purchase totals =	$1,156.03		$1,262.3141	$1,262.31	$1,262.35	$1,262.30