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	$216.93	3.401%	$224.3078	$224.31	$224.30	$224.30
Purchase #2	$38.91	10.780%	$43.1045	$43.10	$43.10	$43.10
Purchase #3	$117.77	8.741%	$128.0643	$128.06	$128.05	$128.10
Purchase #4	$56.26	5.342%	$59.2654	$59.27	$59.25	$59.30
Purchase #5	$200.37	10.627%	$221.6633	$221.66	$221.65	$221.70
Purchase #6	$119.43	11.460%	$133.1167	$133.12	$133.10	$133.10
Purchase #7	$134.40	10.517%	$148.5348	$148.53	$148.55	$148.50
7 purchase totals =	$884.07		$958.0568	$958.05	$958.00	$958.10