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	$20.84	3.827%	$21.6375	$21.64	$21.65	$21.60
Purchase #2	$39.28	11.559%	$43.8204	$43.82	$43.80	$43.80
Purchase #3	$86.93	6.743%	$92.7917	$92.79	$92.80	$92.80
Purchase #4	$32.34	8.414%	$35.0611	$35.06	$35.05	$35.10
Purchase #5	$143.34	10.835%	$158.8709	$158.87	$158.85	$158.90
Purchase #6	$249.30	10.717%	$276.0175	$276.02	$276.00	$276.00
Purchase #7	$222.72	7.123%	$238.5843	$238.58	$238.60	$238.60
7 purchase totals =	$794.75		$866.7834	$866.78	$866.75	$866.80