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	$235.68	7.538%	$253.4456	$253.45	$253.45	$253.40
Purchase #2	$96.56	8.314%	$104.588	$104.59	$104.60	$104.60
Purchase #3	$127.58	8.439%	$138.3465	$138.35	$138.35	$138.30
Purchase #4	$69.87	4.107%	$72.7396	$72.74	$72.75	$72.70
Purchase #5	$244.95	12.440%	$275.4218	$275.42	$275.40	$275.40
Purchase #6	$227.87	3.514%	$235.8774	$235.88	$235.90	$235.90
Purchase #7	$86.39	7.133%	$92.5522	$92.55	$92.55	$92.60
7 purchase totals =	$1,088.90		$1,172.9711	$1,172.98	$1,173.00	$1,172.90