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	$10.71	11.411%	$11.9321	$11.93	$11.95	$11.90
Purchase #2	$178.90	6.427%	$190.3979	$190.40	$190.40	$190.40
Purchase #3	$132.38	3.634%	$137.1907	$137.19	$137.20	$137.20
Purchase #4	$129.72	13.330%	$147.0117	$147.01	$147.00	$147.00
Purchase #5	$39.81	10.623%	$44.039	$44.04	$44.05	$44.00
Purchase #6	$96.57	3.840%	$100.2783	$100.28	$100.30	$100.30
Purchase #7	$144.72	4.608%	$151.3887	$151.39	$151.40	$151.40
7 purchase totals =	$732.81		$782.2384	$782.24	$782.30	$782.20