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	$54.73	8.756%	$59.5222	$59.52	$59.50	$59.50
Purchase #2	$126.88	4.263%	$132.2889	$132.29	$132.30	$132.30
Purchase #3	$62.90	3.640%	$65.1896	$65.19	$65.20	$65.20
Purchase #4	$191.35	5.446%	$201.7709	$201.77	$201.75	$201.80
Purchase #5	$145.89	11.345%	$162.4412	$162.44	$162.45	$162.40
Purchase #6	$185.77	13.851%	$211.501	$211.50	$211.50	$211.50
Purchase #7	$68.62	13.375%	$77.7979	$77.80	$77.80	$77.80
7 purchase totals =	$836.14		$910.5117	$910.51	$910.50	$910.50