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	$118.67	8.460%	$128.7095	$128.71	$128.70	$128.70
Purchase #2	$206.75	11.517%	$230.5614	$230.56	$230.55	$230.60
Purchase #3	$99.85	11.189%	$111.0222	$111.02	$111.00	$111.00
Purchase #4	$191.83	9.586%	$210.2188	$210.22	$210.20	$210.20
Purchase #5	$129.78	13.235%	$146.9564	$146.96	$146.95	$147.00
Purchase #6	$162.89	4.802%	$170.712	$170.71	$170.70	$170.70
Purchase #7	$152.84	12.588%	$172.0795	$172.08	$172.10	$172.10
7 purchase totals =	$1,062.61		$1,170.2598	$1,170.26	$1,170.20	$1,170.30