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	$166.48	8.573%	$180.7523	$180.75	$180.75	$180.80
Purchase #2	$100.40	11.114%	$111.5585	$111.56	$111.55	$111.60
Purchase #3	$78.58	9.448%	$86.0042	$86.00	$86.00	$86.00
Purchase #4	$91.45	8.605%	$99.3193	$99.32	$99.30	$99.30
Purchase #5	$111.28	4.627%	$116.4289	$116.43	$116.45	$116.40
Purchase #6	$128.81	4.207%	$134.229	$134.23	$134.25	$134.20
Purchase #7	$168.83	6.862%	$180.4151	$180.42	$180.40	$180.40
7 purchase totals =	$845.83		$908.7073	$908.71	$908.70	$908.70