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	$68.94	8.436%	$74.7558	$74.76	$74.75	$74.80
Purchase #2	$177.26	4.650%	$185.5026	$185.50	$185.50	$185.50
Purchase #3	$94.63	6.578%	$100.8548	$100.85	$100.85	$100.90
Purchase #4	$52.89	4.788%	$55.4224	$55.42	$55.40	$55.40
Purchase #5	$88.58	9.246%	$96.7701	$96.77	$96.75	$96.80
Purchase #6	$173.27	10.284%	$191.0891	$191.09	$191.10	$191.10
Purchase #7	$183.52	13.760%	$208.7724	$208.77	$208.75	$208.80
7 purchase totals =	$839.09		$913.1672	$913.16	$913.10	$913.30