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	$124.95	4.538%	$130.6202	$130.62	$130.60	$130.60
Purchase #2	$64.51	11.733%	$72.079	$72.08	$72.10	$72.10
Purchase #3	$12.91	13.524%	$14.6559	$14.66	$14.65	$14.70
Purchase #4	$69.66	3.334%	$71.9825	$71.98	$72.00	$72.00
Purchase #5	$183.45	9.477%	$200.8356	$200.84	$200.85	$200.80
Purchase #6	$83.45	11.176%	$92.7764	$92.78	$92.80	$92.80
Purchase #7	$31.76	12.151%	$35.6192	$35.62	$35.60	$35.60
7 purchase totals =	$570.69		$618.5688	$618.58	$618.60	$618.60