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	$74.65	5.575%	$78.8117	$78.81	$78.80	$78.80
Purchase #2	$108.61	5.838%	$114.9507	$114.95	$114.95	$115.00
Purchase #3	$223.66	4.748%	$234.2794	$234.28	$234.30	$234.30
Purchase #4	$95.77	4.145%	$99.7397	$99.74	$99.75	$99.70
Purchase #5	$217.47	9.852%	$238.8951	$238.90	$238.90	$238.90
Purchase #6	$106.50	9.599%	$116.7229	$116.72	$116.70	$116.70
Purchase #7	$134.32	12.224%	$150.7393	$150.74	$150.75	$150.70
7 purchase totals =	$960.98		$1,034.1388	$1,034.14	$1,034.15	$1,034.10