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	$209.68	3.210%	$216.4107	$216.41	$216.40	$216.40
Purchase #2	$151.70	5.650%	$160.2711	$160.27	$160.25	$160.30
Purchase #3	$172.28	4.343%	$179.7621	$179.76	$179.75	$179.80
Purchase #4	$48.26	4.768%	$50.561	$50.56	$50.55	$50.60
Purchase #5	$158.85	12.446%	$178.6205	$178.62	$178.60	$178.60
Purchase #6	$67.44	4.606%	$70.5463	$70.55	$70.55	$70.50
Purchase #7	$135.59	6.424%	$144.3003	$144.30	$144.30	$144.30
7 purchase totals =	$943.80		$1,000.4720	$1,000.47	$1,000.40	$1,000.50