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	$156.56	5.680%	$165.4526	$165.45	$165.45	$165.50
Purchase #2	$79.27	3.497%	$82.0421	$82.04	$82.05	$82.00
Purchase #3	$236.60	8.162%	$255.9113	$255.91	$255.90	$255.90
Purchase #4	$64.67	7.718%	$69.6612	$69.66	$69.65	$69.70
Purchase #5	$145.93	8.719%	$158.6536	$158.65	$158.65	$158.70
Purchase #6	$122.61	7.761%	$132.1258	$132.13	$132.15	$132.10
Purchase #7	$99.51	10.113%	$109.5734	$109.57	$109.55	$109.60
7 purchase totals =	$905.15		$973.4200	$973.41	$973.40	$973.50