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	$145.77	11.579%	$162.6487	$162.65	$162.65	$162.60
Purchase #2	$24.47	4.323%	$25.5278	$25.53	$25.55	$25.50
Purchase #3	$135.89	12.133%	$152.3775	$152.38	$152.40	$152.40
Purchase #4	$131.37	11.500%	$146.4776	$146.48	$146.50	$146.50
Purchase #5	$116.46	9.269%	$127.2547	$127.25	$127.25	$127.30
Purchase #6	$97.55	12.767%	$110.0042	$110.00	$110.00	$110.00
Purchase #7	$171.72	9.662%	$188.3116	$188.31	$188.30	$188.30
7 purchase totals =	$823.23		$912.6021	$912.60	$912.65	$912.60