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	$89.68	3.254%	$92.5982	$92.60	$92.60	$92.60
Purchase #2	$145.39	6.164%	$154.3518	$154.35	$154.35	$154.40
Purchase #3	$10.36	13.740%	$11.7835	$11.78	$11.80	$11.80
Purchase #4	$16.70	3.188%	$17.2324	$17.23	$17.25	$17.20
Purchase #5	$71.26	10.679%	$78.8699	$78.87	$78.85	$78.90
Purchase #6	$42.94	7.714%	$46.2524	$46.25	$46.25	$46.30
Purchase #7	$231.40	6.864%	$247.2833	$247.28	$247.30	$247.30
7 purchase totals =	$607.73		$648.3715	$648.36	$648.40	$648.50