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	$83.25	13.211%	$94.2482	$94.25	$94.25	$94.20
Purchase #2	$148.68	3.795%	$154.3224	$154.32	$154.30	$154.30
Purchase #3	$219.76	4.600%	$229.869	$229.87	$229.85	$229.90
Purchase #4	$226.28	4.222%	$235.8335	$235.83	$235.85	$235.80
Purchase #5	$69.25	4.823%	$72.5899	$72.59	$72.60	$72.60
Purchase #6	$121.48	12.337%	$136.467	$136.47	$136.45	$136.50
Purchase #7	$52.51	13.222%	$59.4529	$59.45	$59.45	$59.50
7 purchase totals =	$921.21		$982.7829	$982.78	$982.75	$982.80