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	$116.84	5.279%	$123.008	$123.01	$123.00	$123.00
Purchase #2	$91.27	6.553%	$97.2509	$97.25	$97.25	$97.30
Purchase #3	$103.69	7.414%	$111.3776	$111.38	$111.40	$111.40
Purchase #4	$109.48	4.680%	$114.6037	$114.60	$114.60	$114.60
Purchase #5	$242.91	11.825%	$271.6341	$271.63	$271.65	$271.60
Purchase #6	$190.71	13.689%	$216.8163	$216.82	$216.80	$216.80
Purchase #7	$37.92	7.582%	$40.7951	$40.80	$40.80	$40.80
7 purchase totals =	$892.82		$975.4857	$975.49	$975.50	$975.50