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	$53.79	11.746%	$60.1082	$60.11	$60.10	$60.10
Purchase #2	$102.57	9.751%	$112.5716	$112.57	$112.55	$112.60
Purchase #3	$33.27	12.377%	$37.3878	$37.39	$37.40	$37.40
Purchase #4	$101.97	3.622%	$105.6634	$105.66	$105.65	$105.70
Purchase #5	$249.66	8.735%	$271.4678	$271.47	$271.45	$271.50
Purchase #6	$34.35	8.537%	$37.2825	$37.28	$37.30	$37.30
Purchase #7	$163.70	13.274%	$185.4295	$185.43	$185.45	$185.40
7 purchase totals =	$739.31		$809.9108	$809.91	$809.90	$810.00