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	$80.41	6.770%	$85.8538	$85.85	$85.85	$85.90
Purchase #2	$46.52	8.720%	$50.5765	$50.58	$50.60	$50.60
Purchase #3	$103.77	10.492%	$114.6575	$114.66	$114.65	$114.70
Purchase #4	$238.64	11.335%	$265.6898	$265.69	$265.70	$265.70
Purchase #5	$131.34	11.774%	$146.804	$146.80	$146.80	$146.80
Purchase #6	$230.89	7.601%	$248.4399	$248.44	$248.45	$248.40
Purchase #7	$250.68	7.611%	$269.7593	$269.76	$269.75	$269.80
7 purchase totals =	$1,082.25		$1,181.7808	$1,181.78	$1,181.80	$1,181.90