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	$124.81	4.364%	$130.2567	$130.26	$130.25	$130.30
Purchase #2	$34.38	5.643%	$36.3201	$36.32	$36.30	$36.30
Purchase #3	$38.80	12.517%	$43.6566	$43.66	$43.65	$43.70
Purchase #4	$14.92	4.157%	$15.5402	$15.54	$15.55	$15.50
Purchase #5	$119.58	9.717%	$131.1996	$131.20	$131.20	$131.20
Purchase #6	$116.39	9.370%	$127.2957	$127.30	$127.30	$127.30
Purchase #7	$36.51	5.802%	$38.6283	$38.63	$38.65	$38.60
7 purchase totals =	$485.39		$522.8972	$522.91	$522.90	$522.90