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	$76.92	11.181%	$85.5204	$85.52	$85.50	$85.50
Purchase #2	$173.38	6.772%	$185.1213	$185.12	$185.10	$185.10
Purchase #3	$121.75	3.150%	$125.5851	$125.59	$125.60	$125.60
Purchase #4	$114.41	4.142%	$119.1489	$119.15	$119.15	$119.10
Purchase #5	$173.74	12.125%	$194.806	$194.81	$194.80	$194.80
Purchase #6	$182.51	3.120%	$188.2043	$188.20	$188.20	$188.20
Purchase #7	$169.64	10.328%	$187.1604	$187.16	$187.15	$187.20
7 purchase totals =	$1,012.35		$1,085.5464	$1,085.55	$1,085.50	$1,085.50