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	$56.46	5.415%	$59.5173	$59.52	$59.50	$59.50
Purchase #2	$194.92	3.447%	$201.6389	$201.64	$201.65	$201.60
Purchase #3	$54.32	11.155%	$60.3794	$60.38	$60.40	$60.40
Purchase #4	$40.87	3.503%	$42.3017	$42.30	$42.30	$42.30
Purchase #5	$218.26	13.385%	$247.4741	$247.47	$247.45	$247.50
Purchase #6	$17.44	4.849%	$18.2857	$18.29	$18.30	$18.30
Purchase #7	$96.78	3.705%	$100.3657	$100.37	$100.35	$100.40
7 purchase totals =	$679.05		$729.9628	$729.97	$729.95	$730.00