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	$225.47	12.381%	$253.3854	$253.39	$253.40	$253.40
Purchase #2	$54.72	3.557%	$56.6664	$56.67	$56.65	$56.70
Purchase #3	$146.89	13.656%	$166.9493	$166.95	$166.95	$166.90
Purchase #4	$87.33	13.636%	$99.2383	$99.24	$99.25	$99.20
Purchase #5	$19.98	3.271%	$20.6335	$20.63	$20.65	$20.60
Purchase #6	$119.41	7.581%	$128.4625	$128.46	$128.45	$128.50
Purchase #7	$225.66	4.452%	$235.7064	$235.71	$235.70	$235.70
7 purchase totals =	$879.46		$961.0418	$961.05	$961.05	$961.00