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	$188.56	12.815%	$212.724	$212.72	$212.70	$212.70
Purchase #2	$56.89	9.624%	$62.3651	$62.37	$62.35	$62.40
Purchase #3	$159.36	6.404%	$169.5654	$169.57	$169.55	$169.60
Purchase #4	$79.30	9.753%	$87.0341	$87.03	$87.05	$87.00
Purchase #5	$101.82	9.462%	$111.4542	$111.45	$111.45	$111.50
Purchase #6	$100.32	11.185%	$111.5408	$111.54	$111.55	$111.50
Purchase #7	$137.72	4.245%	$143.5662	$143.57	$143.55	$143.60
7 purchase totals =	$823.97		$898.2498	$898.25	$898.20	$898.30