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	$196.95	13.462%	$223.4634	$223.46	$223.45	$223.50
Purchase #2	$151.77	10.221%	$167.2824	$167.28	$167.30	$167.30
Purchase #3	$211.49	4.187%	$220.3451	$220.35	$220.35	$220.30
Purchase #4	$40.93	9.435%	$44.7917	$44.79	$44.80	$44.80
Purchase #5	$92.81	7.491%	$99.7624	$99.76	$99.75	$99.80
Purchase #6	$52.94	10.615%	$58.5596	$58.56	$58.55	$58.60
Purchase #7	$152.59	8.434%	$165.4594	$165.46	$165.45	$165.50
7 purchase totals =	$899.48		$979.6640	$979.66	$979.65	$979.80