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	$64.56	12.767%	$72.8024	$72.80	$72.80	$72.80
Purchase #2	$65.48	12.280%	$73.5209	$73.52	$73.50	$73.50
Purchase #3	$66.27	13.543%	$75.2449	$75.24	$75.25	$75.20
Purchase #4	$19.72	11.173%	$21.9233	$21.92	$21.90	$21.90
Purchase #5	$55.81	5.553%	$58.9091	$58.91	$58.90	$58.90
Purchase #6	$233.82	10.405%	$258.149	$258.15	$258.15	$258.10
Purchase #7	$19.28	6.228%	$20.4808	$20.48	$20.50	$20.50
7 purchase totals =	$524.94		$581.0304	$581.02	$581.00	$580.90