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	$137.74	10.844%	$152.6765	$152.68	$152.70	$152.70
Purchase #2	$193.42	10.686%	$214.0889	$214.09	$214.10	$214.10
Purchase #3	$98.72	7.306%	$105.9325	$105.93	$105.95	$105.90
Purchase #4	$122.41	6.518%	$130.3887	$130.39	$130.40	$130.40
Purchase #5	$174.62	8.323%	$189.1536	$189.15	$189.15	$189.20
Purchase #6	$244.66	12.230%	$274.5819	$274.58	$274.60	$274.60
Purchase #7	$83.88	6.407%	$89.2542	$89.25	$89.25	$89.30
7 purchase totals =	$1,055.45		$1,156.0763	$1,156.07	$1,156.15	$1,156.20