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	$58.58	5.655%	$61.8927	$61.89	$61.90	$61.90
Purchase #2	$123.72	3.208%	$127.6889	$127.69	$127.70	$127.70
Purchase #3	$107.28	3.721%	$111.2719	$111.27	$111.25	$111.30
Purchase #4	$211.30	10.264%	$232.9878	$232.99	$233.00	$233.00
Purchase #5	$36.31	9.457%	$39.7438	$39.74	$39.75	$39.70
Purchase #6	$7.71	12.494%	$8.6733	$8.67	$8.65	$8.70
Purchase #7	$29.77	8.207%	$32.2132	$32.21	$32.20	$32.20
7 purchase totals =	$574.67		$614.4716	$614.46	$614.45	$614.50