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	$216.74	3.179%	$223.6302	$223.63	$223.65	$223.60
Purchase #2	$12.41	11.863%	$13.8822	$13.88	$13.90	$13.90
Purchase #3	$165.30	8.564%	$179.4563	$179.46	$179.45	$179.50
Purchase #4	$105.72	11.188%	$117.548	$117.55	$117.55	$117.50
Purchase #5	$20.88	6.649%	$22.2683	$22.27	$22.25	$22.30
Purchase #6	$238.30	8.474%	$258.4935	$258.49	$258.50	$258.50
Purchase #7	$95.54	4.797%	$100.1231	$100.12	$100.10	$100.10
7 purchase totals =	$854.89		$915.4016	$915.40	$915.40	$915.40