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	$44.51	8.564%	$48.3218	$48.32	$48.30	$48.30
Purchase #2	$179.42	3.510%	$185.7176	$185.72	$185.70	$185.70
Purchase #3	$146.26	3.130%	$150.8379	$150.84	$150.85	$150.80
Purchase #4	$195.99	6.603%	$208.9312	$208.93	$208.95	$208.90
Purchase #5	$154.49	11.511%	$172.2733	$172.27	$172.25	$172.30
Purchase #6	$54.26	6.626%	$57.8553	$57.86	$57.85	$57.90
Purchase #7	$104.25	4.442%	$108.8808	$108.88	$108.90	$108.90
7 purchase totals =	$879.18		$932.8179	$932.82	$932.80	$932.80