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	$12.75	10.578%	$14.0987	$14.10	$14.10	$14.10
Purchase #2	$99.41	4.678%	$104.0604	$104.06	$104.05	$104.10
Purchase #3	$133.50	3.291%	$137.8935	$137.89	$137.90	$137.90
Purchase #4	$211.52	8.413%	$229.3152	$229.32	$229.30	$229.30
Purchase #5	$58.57	13.539%	$66.4998	$66.50	$66.50	$66.50
Purchase #6	$127.97	7.157%	$137.1288	$137.13	$137.15	$137.10
Purchase #7	$157.52	6.317%	$167.4705	$167.47	$167.45	$167.50
7 purchase totals =	$801.24		$856.4669	$856.47	$856.45	$856.50