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	$196.83	8.267%	$213.1019	$213.10	$213.10	$213.10
Purchase #2	$169.76	4.222%	$176.9273	$176.93	$176.95	$176.90
Purchase #3	$157.96	9.366%	$172.7545	$172.75	$172.75	$172.80
Purchase #4	$198.35	3.482%	$205.2565	$205.26	$205.25	$205.30
Purchase #5	$92.33	12.512%	$103.8823	$103.88	$103.90	$103.90
Purchase #6	$230.72	5.520%	$243.4557	$243.46	$243.45	$243.50
Purchase #7	$19.88	4.408%	$20.7563	$20.76	$20.75	$20.80
7 purchase totals =	$1,065.83		$1,136.1345	$1,136.14	$1,136.15	$1,136.30