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	$54.52	8.557%	$59.1853	$59.19	$59.20	$59.20
Purchase #2	$50.72	10.196%	$55.8914	$55.89	$55.90	$55.90
Purchase #3	$27.26	11.803%	$30.4775	$30.48	$30.50	$30.50
Purchase #4	$247.90	9.647%	$271.8149	$271.81	$271.80	$271.80
Purchase #5	$238.92	8.477%	$259.1732	$259.17	$259.15	$259.20
Purchase #6	$154.35	10.713%	$170.8855	$170.89	$170.90	$170.90
Purchase #7	$100.31	11.412%	$111.7574	$111.76	$111.75	$111.80
7 purchase totals =	$873.98		$959.1852	$959.19	$959.20	$959.30