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	$185.70	12.548%	$209.0016	$209.00	$209.00	$209.00
Purchase #2	$224.44	13.137%	$253.9247	$253.92	$253.90	$253.90
Purchase #3	$175.65	5.201%	$184.7856	$184.79	$184.80	$184.80
Purchase #4	$25.27	12.695%	$28.478	$28.48	$28.50	$28.50
Purchase #5	$173.54	3.490%	$179.5965	$179.60	$179.60	$179.60
Purchase #6	$137.27	4.723%	$143.7533	$143.75	$143.75	$143.80
Purchase #7	$61.92	8.112%	$66.943	$66.94	$66.95	$66.90
7 purchase totals =	$983.79		$1,066.4827	$1,066.48	$1,066.50	$1,066.50