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	$196.62	10.314%	$216.8994	$216.90	$216.90	$216.90
Purchase #2	$59.73	12.426%	$67.152	$67.15	$67.15	$67.20
Purchase #3	$19.98	3.575%	$20.6943	$20.69	$20.70	$20.70
Purchase #4	$32.28	3.535%	$33.4211	$33.42	$33.40	$33.40
Purchase #5	$23.44	11.196%	$26.0643	$26.06	$26.05	$26.10
Purchase #6	$173.85	9.346%	$190.098	$190.10	$190.10	$190.10
Purchase #7	$51.26	11.656%	$57.2349	$57.23	$57.25	$57.20
7 purchase totals =	$557.16		$611.5640	$611.55	$611.55	$611.60