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	$61.65	5.147%	$64.8231	$64.82	$64.80	$64.80
Purchase #2	$26.95	10.345%	$29.738	$29.74	$29.75	$29.70
Purchase #3	$114.69	7.512%	$123.3055	$123.31	$123.30	$123.30
Purchase #4	$122.27	12.571%	$137.6406	$137.64	$137.65	$137.60
Purchase #5	$101.53	7.136%	$108.7752	$108.78	$108.80	$108.80
Purchase #6	$62.78	3.161%	$64.7645	$64.76	$64.75	$64.80
Purchase #7	$121.60	4.739%	$127.3626	$127.36	$127.35	$127.40
7 purchase totals =	$611.47		$656.4095	$656.41	$656.40	$656.40