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	$54.51	8.775%	$59.2933	$59.29	$59.30	$59.30
Purchase #2	$16.33	3.719%	$16.9373	$16.94	$16.95	$16.90
Purchase #3	$17.27	9.306%	$18.8771	$18.88	$18.90	$18.90
Purchase #4	$83.97	6.713%	$89.6069	$89.61	$89.60	$89.60
Purchase #5	$49.75	13.501%	$56.4667	$56.47	$56.45	$56.50
Purchase #6	$153.26	3.394%	$158.4616	$158.46	$158.45	$158.50
Purchase #7	$137.86	7.262%	$147.8714	$147.87	$147.85	$147.90
7 purchase totals =	$512.95		$547.5143	$547.52	$547.50	$547.60