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	$53.65	10.147%	$59.0939	$59.09	$59.10	$59.10
Purchase #2	$247.69	12.619%	$278.946	$278.95	$278.95	$278.90
Purchase #3	$92.52	11.803%	$103.4401	$103.44	$103.45	$103.40
Purchase #4	$133.49	4.440%	$139.417	$139.42	$139.40	$139.40
Purchase #5	$156.62	3.842%	$162.6373	$162.64	$162.65	$162.60
Purchase #6	$85.46	3.381%	$88.3494	$88.35	$88.35	$88.30
Purchase #7	$50.73	4.721%	$53.125	$53.13	$53.15	$53.10
7 purchase totals =	$820.16		$885.0087	$885.02	$885.05	$884.80