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	$124.25	13.232%	$140.6908	$140.69	$140.70	$140.70
Purchase #2	$77.89	6.259%	$82.7651	$82.77	$82.75	$82.80
Purchase #3	$162.97	4.711%	$170.6475	$170.65	$170.65	$170.60
Purchase #4	$30.60	5.182%	$32.1857	$32.19	$32.20	$32.20
Purchase #5	$34.88	7.356%	$37.4458	$37.45	$37.45	$37.40
Purchase #6	$233.28	12.781%	$263.0955	$263.10	$263.10	$263.10
Purchase #7	$19.82	5.327%	$20.8758	$20.88	$20.90	$20.90
7 purchase totals =	$683.69		$747.7062	$747.73	$747.75	$747.70