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	$60.52	3.774%	$62.804	$62.80	$62.80	$62.80
Purchase #2	$13.44	4.471%	$14.0409	$14.04	$14.05	$14.00
Purchase #3	$68.60	11.539%	$76.5158	$76.52	$76.50	$76.50
Purchase #4	$36.75	13.152%	$41.5834	$41.58	$41.60	$41.60
Purchase #5	$128.36	12.268%	$144.1072	$144.11	$144.10	$144.10
Purchase #6	$54.50	12.633%	$61.385	$61.39	$61.40	$61.40
Purchase #7	$118.84	13.230%	$134.5625	$134.56	$134.55	$134.60
7 purchase totals =	$481.01		$534.9988	$535.00	$535.00	$535.00