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	$85.99	13.755%	$97.8179	$97.82	$97.80	$97.80
Purchase #2	$19.38	12.643%	$21.8302	$21.83	$21.85	$21.80
Purchase #3	$13.34	6.258%	$14.1748	$14.17	$14.15	$14.20
Purchase #4	$156.41	10.467%	$172.7814	$172.78	$172.80	$172.80
Purchase #5	$53.64	11.823%	$59.9819	$59.98	$60.00	$60.00
Purchase #6	$48.44	7.245%	$51.9495	$51.95	$51.95	$51.90
Purchase #7	$11.28	10.824%	$12.5009	$12.50	$12.50	$12.50
7 purchase totals =	$388.48		$431.0366	$431.03	$431.05	$431.00