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	$120.64	7.127%	$129.238	$129.24	$129.25	$129.20
Purchase #2	$99.48	11.749%	$111.1679	$111.17	$111.15	$111.20
Purchase #3	$195.89	13.769%	$222.8621	$222.86	$222.85	$222.90
Purchase #4	$94.36	12.185%	$105.8578	$105.86	$105.85	$105.90
Purchase #5	$54.76	9.790%	$60.121	$60.12	$60.10	$60.10
Purchase #6	$146.85	4.612%	$153.6227	$153.62	$153.60	$153.60
Purchase #7	$199.44	7.556%	$214.5097	$214.51	$214.50	$214.50
7 purchase totals =	$911.42		$997.3792	$997.38	$997.30	$997.40