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	$48.72	11.708%	$54.4241	$54.42	$54.40	$54.40
Purchase #2	$106.89	5.505%	$112.7743	$112.77	$112.75	$112.80
Purchase #3	$218.57	10.263%	$241.0018	$241.00	$241.00	$241.00
Purchase #4	$133.54	8.177%	$144.4596	$144.46	$144.45	$144.50
Purchase #5	$64.80	8.619%	$70.3851	$70.39	$70.40	$70.40
Purchase #6	$99.40	13.827%	$113.144	$113.14	$113.15	$113.10
Purchase #7	$34.32	9.631%	$37.6254	$37.63	$37.65	$37.60
7 purchase totals =	$706.24		$773.8143	$773.81	$773.80	$773.80