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	$244.26	5.417%	$257.4916	$257.49	$257.50	$257.50
Purchase #2	$60.72	13.773%	$69.083	$69.08	$69.10	$69.10
Purchase #3	$103.72	10.188%	$114.287	$114.29	$114.30	$114.30
Purchase #4	$81.37	10.133%	$89.6152	$89.62	$89.60	$89.60
Purchase #5	$20.47	11.301%	$22.7833	$22.78	$22.80	$22.80
Purchase #6	$32.39	11.451%	$36.099	$36.10	$36.10	$36.10
Purchase #7	$132.76	10.803%	$147.1021	$147.10	$147.10	$147.10
7 purchase totals =	$675.69		$736.4612	$736.46	$736.50	$736.50