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	$58.87	4.123%	$61.2972	$61.30	$61.30	$61.30
Purchase #2	$89.42	12.363%	$100.475	$100.48	$100.50	$100.50
Purchase #3	$35.62	4.663%	$37.281	$37.28	$37.30	$37.30
Purchase #4	$47.49	3.456%	$49.1313	$49.13	$49.15	$49.10
Purchase #5	$29.32	4.323%	$30.5875	$30.59	$30.60	$30.60
Purchase #6	$32.28	4.791%	$33.8265	$33.83	$33.85	$33.80
Purchase #7	$166.57	11.845%	$186.3002	$186.30	$186.30	$186.30
7 purchase totals =	$459.57		$498.8987	$498.91	$499.00	$498.90