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	$43.62	11.773%	$48.7554	$48.76	$48.75	$48.80
Purchase #2	$11.32	8.531%	$12.2857	$12.29	$12.30	$12.30
Purchase #3	$165.72	12.710%	$186.783	$186.78	$186.80	$186.80
Purchase #4	$229.54	6.851%	$245.2658	$245.27	$245.25	$245.30
Purchase #5	$140.59	10.323%	$155.1031	$155.10	$155.10	$155.10
Purchase #6	$101.51	4.306%	$105.881	$105.88	$105.90	$105.90
Purchase #7	$50.46	12.580%	$56.8079	$56.81	$56.80	$56.80
7 purchase totals =	$742.76		$810.8819	$810.89	$810.90	$811.00