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	$208.56	11.856%	$233.2869	$233.29	$233.30	$233.30
Purchase #2	$201.98	8.524%	$219.1968	$219.20	$219.20	$219.20
Purchase #3	$226.57	6.677%	$241.6981	$241.70	$241.70	$241.70
Purchase #4	$100.79	8.604%	$109.462	$109.46	$109.45	$109.50
Purchase #5	$101.51	10.206%	$111.8701	$111.87	$111.85	$111.90
Purchase #6	$54.88	4.621%	$57.416	$57.42	$57.40	$57.40
Purchase #7	$207.31	5.560%	$218.8364	$218.84	$218.85	$218.80
7 purchase totals =	$1,101.60		$1,191.7663	$1,191.78	$1,191.75	$1,191.80