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	$125.80	12.736%	$141.8219	$141.82	$141.80	$141.80
Purchase #2	$149.27	12.739%	$168.2855	$168.29	$168.30	$168.30
Purchase #3	$115.32	13.832%	$131.2711	$131.27	$131.25	$131.30
Purchase #4	$139.71	8.157%	$151.1061	$151.11	$151.10	$151.10
Purchase #5	$119.79	6.706%	$127.8231	$127.82	$127.80	$127.80
Purchase #6	$211.54	13.147%	$239.3512	$239.35	$239.35	$239.40
Purchase #7	$32.82	3.588%	$33.9976	$34.00	$34.00	$34.00
7 purchase totals =	$894.25		$993.6565	$993.66	$993.60	$993.70