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	$151.40	5.487%	$159.7073	$159.71	$159.70	$159.70
Purchase #2	$179.28	11.366%	$199.657	$199.66	$199.65	$199.70
Purchase #3	$120.57	5.760%	$127.5148	$127.51	$127.50	$127.50
Purchase #4	$95.44	10.654%	$105.6082	$105.61	$105.60	$105.60
Purchase #5	$56.99	13.436%	$64.6472	$64.65	$64.65	$64.60
Purchase #6	$33.45	11.721%	$37.3707	$37.37	$37.35	$37.40
Purchase #7	$220.77	3.395%	$228.2651	$228.27	$228.25	$228.30
7 purchase totals =	$857.90		$922.7703	$922.78	$922.70	$922.80