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	$187.80	3.415%	$194.2134	$194.21	$194.20	$194.20
Purchase #2	$167.52	4.560%	$175.1589	$175.16	$175.15	$175.20
Purchase #3	$156.58	10.453%	$172.9473	$172.95	$172.95	$172.90
Purchase #4	$39.70	6.514%	$42.2861	$42.29	$42.30	$42.30
Purchase #5	$10.97	6.423%	$11.6746	$11.67	$11.65	$11.70
Purchase #6	$118.48	7.399%	$127.2463	$127.25	$127.25	$127.20
Purchase #7	$17.96	12.156%	$20.1432	$20.14	$20.15	$20.10
7 purchase totals =	$699.01		$743.6698	$743.67	$743.65	$743.60