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	$67.52	4.113%	$70.2971	$70.30	$70.30	$70.30
Purchase #2	$93.54	6.505%	$99.6248	$99.62	$99.60	$99.60
Purchase #3	$160.58	11.706%	$179.3775	$179.38	$179.40	$179.40
Purchase #4	$9.73	12.483%	$10.9446	$10.94	$10.95	$10.90
Purchase #5	$42.92	12.514%	$48.291	$48.29	$48.30	$48.30
Purchase #6	$220.97	5.568%	$233.2736	$233.27	$233.25	$233.30
Purchase #7	$145.52	9.856%	$159.8625	$159.86	$159.85	$159.90
7 purchase totals =	$740.78		$801.6711	$801.66	$801.65	$801.70