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	$22.32	9.794%	$24.506	$24.51	$24.50	$24.50
Purchase #2	$86.90	9.780%	$95.3988	$95.40	$95.40	$95.40
Purchase #3	$92.45	3.238%	$95.4435	$95.44	$95.45	$95.40
Purchase #4	$179.86	10.401%	$198.5672	$198.57	$198.55	$198.60
Purchase #5	$216.40	3.130%	$223.1733	$223.17	$223.15	$223.20
Purchase #6	$148.94	11.823%	$166.5492	$166.55	$166.55	$166.50
Purchase #7	$247.69	12.693%	$279.1293	$279.13	$279.15	$279.10
7 purchase totals =	$994.56		$1,082.7673	$1,082.77	$1,082.75	$1,082.70