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	$94.63	10.859%	$104.9059	$104.91	$104.90	$104.90
Purchase #2	$137.45	3.253%	$141.9212	$141.92	$141.90	$141.90
Purchase #3	$118.51	7.436%	$127.3224	$127.32	$127.30	$127.30
Purchase #4	$137.39	3.212%	$141.803	$141.80	$141.80	$141.80
Purchase #5	$200.73	4.343%	$209.4477	$209.45	$209.45	$209.40
Purchase #6	$134.42	12.689%	$151.4766	$151.48	$151.50	$151.50
Purchase #7	$92.88	13.331%	$105.2618	$105.26	$105.25	$105.30
7 purchase totals =	$916.01		$982.1386	$982.14	$982.10	$982.10