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	$52.65	12.472%	$59.2165	$59.22	$59.20	$59.20
Purchase #2	$184.81	12.715%	$208.3086	$208.31	$208.30	$208.30
Purchase #3	$231.25	5.848%	$244.7735	$244.77	$244.75	$244.80
Purchase #4	$153.59	9.868%	$168.7463	$168.75	$168.75	$168.70
Purchase #5	$55.45	4.463%	$57.9247	$57.92	$57.90	$57.90
Purchase #6	$111.64	11.862%	$124.8827	$124.88	$124.90	$124.90
Purchase #7	$41.89	3.642%	$43.4156	$43.42	$43.40	$43.40
7 purchase totals =	$831.28		$907.2679	$907.27	$907.20	$907.20