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	$210.37	9.431%	$230.21	$230.21	$230.20	$230.20
Purchase #2	$181.46	3.483%	$187.7803	$187.78	$187.80	$187.80
Purchase #3	$89.62	12.466%	$100.792	$100.79	$100.80	$100.80
Purchase #4	$198.71	6.784%	$212.1905	$212.19	$212.20	$212.20
Purchase #5	$211.25	10.485%	$233.3996	$233.40	$233.40	$233.40
Purchase #6	$29.31	11.312%	$32.6255	$32.63	$32.65	$32.60
Purchase #7	$30.85	9.766%	$33.8628	$33.86	$33.85	$33.90
7 purchase totals =	$951.57		$1,030.8607	$1,030.86	$1,030.90	$1,030.90