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	$105.32	11.622%	$117.5603	$117.56	$117.55	$117.60
Purchase #2	$55.55	5.851%	$58.8002	$58.80	$58.80	$58.80
Purchase #3	$18.26	8.178%	$19.7533	$19.75	$19.75	$19.80
Purchase #4	$79.76	6.666%	$85.0768	$85.08	$85.10	$85.10
Purchase #5	$9.46	7.704%	$10.1888	$10.19	$10.20	$10.20
Purchase #6	$90.84	10.795%	$100.6462	$100.65	$100.65	$100.60
Purchase #7	$69.35	4.326%	$72.3501	$72.35	$72.35	$72.40
7 purchase totals =	$428.54		$464.3757	$464.38	$464.40	$464.50