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	$100.39	5.353%	$105.7639	$105.76	$105.75	$105.80
Purchase #2	$212.88	4.606%	$222.6853	$222.69	$222.70	$222.70
Purchase #3	$217.91	10.855%	$241.5641	$241.56	$241.55	$241.60
Purchase #4	$70.99	4.616%	$74.2669	$74.27	$74.25	$74.30
Purchase #5	$123.59	3.251%	$127.6079	$127.61	$127.60	$127.60
Purchase #6	$115.30	4.624%	$120.6315	$120.63	$120.65	$120.60
Purchase #7	$132.98	12.358%	$149.4137	$149.41	$149.40	$149.40
7 purchase totals =	$974.04		$1,041.9333	$1,041.93	$1,041.90	$1,042.00