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	$57.37	11.332%	$63.8712	$63.87	$63.85	$63.90
Purchase #2	$109.60	4.343%	$114.3599	$114.36	$114.35	$114.40
Purchase #3	$133.48	10.240%	$147.1484	$147.15	$147.15	$147.10
Purchase #4	$175.47	7.793%	$189.1444	$189.14	$189.15	$189.10
Purchase #5	$146.28	7.175%	$156.7756	$156.78	$156.80	$156.80
Purchase #6	$97.91	7.205%	$104.9644	$104.96	$104.95	$105.00
Purchase #7	$94.78	5.570%	$100.0592	$100.06	$100.05	$100.10
7 purchase totals =	$814.89		$876.3231	$876.32	$876.30	$876.40