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	$99.27	10.362%	$109.5564	$109.56	$109.55	$109.60
Purchase #2	$159.29	5.341%	$167.7977	$167.80	$167.80	$167.80
Purchase #3	$32.79	9.782%	$35.9975	$36.00	$36.00	$36.00
Purchase #4	$34.51	7.583%	$37.1269	$37.13	$37.15	$37.10
Purchase #5	$176.58	8.523%	$191.6299	$191.63	$191.65	$191.60
Purchase #6	$236.78	3.419%	$244.8755	$244.88	$244.90	$244.90
Purchase #7	$118.68	13.291%	$134.4538	$134.45	$134.45	$134.50
7 purchase totals =	$857.90		$921.4377	$921.45	$921.50	$921.50