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	$140.39	10.741%	$155.4693	$155.47	$155.45	$155.50
Purchase #2	$242.78	6.784%	$259.2502	$259.25	$259.25	$259.30
Purchase #3	$11.55	3.129%	$11.9114	$11.91	$11.90	$11.90
Purchase #4	$177.31	13.468%	$201.1901	$201.19	$201.20	$201.20
Purchase #5	$122.43	3.790%	$127.0701	$127.07	$127.05	$127.10
Purchase #6	$89.82	10.830%	$99.5475	$99.55	$99.55	$99.50
Purchase #7	$211.92	4.350%	$221.1385	$221.14	$221.15	$221.10
7 purchase totals =	$996.20		$1,075.5771	$1,075.58	$1,075.55	$1,075.60