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	$45.89	13.364%	$52.0227	$52.02	$52.00	$52.00
Purchase #2	$134.52	11.565%	$150.0772	$150.08	$150.10	$150.10
Purchase #3	$62.91	4.625%	$65.8196	$65.82	$65.80	$65.80
Purchase #4	$108.35	7.670%	$116.6604	$116.66	$116.65	$116.70
Purchase #5	$123.73	10.800%	$137.0928	$137.09	$137.10	$137.10
Purchase #6	$70.96	5.174%	$74.6315	$74.63	$74.65	$74.60
Purchase #7	$160.82	5.693%	$169.9755	$169.98	$170.00	$170.00
7 purchase totals =	$707.18		$766.2797	$766.28	$766.30	$766.30