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	$207.32	6.455%	$220.7025	$220.70	$220.70	$220.70
Purchase #2	$77.65	10.122%	$85.5097	$85.51	$85.50	$85.50
Purchase #3	$212.68	3.573%	$220.2791	$220.28	$220.30	$220.30
Purchase #4	$59.49	3.125%	$61.3491	$61.35	$61.35	$61.30
Purchase #5	$34.92	8.839%	$38.0066	$38.01	$38.00	$38.00
Purchase #6	$154.64	11.425%	$172.3076	$172.31	$172.30	$172.30
Purchase #7	$103.43	7.421%	$111.1055	$111.11	$111.10	$111.10
7 purchase totals =	$850.13		$909.2601	$909.27	$909.25	$909.20