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	$122.27	7.520%	$131.4647	$131.46	$131.45	$131.50
Purchase #2	$116.77	13.607%	$132.6589	$132.66	$132.65	$132.70
Purchase #3	$151.75	8.849%	$165.1784	$165.18	$165.20	$165.20
Purchase #4	$96.43	13.640%	$109.5831	$109.58	$109.60	$109.60
Purchase #5	$197.65	9.848%	$217.1146	$217.11	$217.10	$217.10
Purchase #6	$179.41	9.664%	$196.7482	$196.75	$196.75	$196.70
Purchase #7	$38.42	6.590%	$40.9519	$40.95	$40.95	$41.00
7 purchase totals =	$902.70		$993.6998	$993.69	$993.70	$993.80