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	$170.51	4.503%	$178.1881	$178.19	$178.20	$178.20
Purchase #2	$162.82	8.127%	$176.0524	$176.05	$176.05	$176.10
Purchase #3	$187.60	4.580%	$196.1921	$196.19	$196.20	$196.20
Purchase #4	$35.62	3.846%	$36.9899	$36.99	$37.00	$37.00
Purchase #5	$141.85	12.472%	$159.5415	$159.54	$159.55	$159.50
Purchase #6	$133.50	9.426%	$146.0837	$146.08	$146.10	$146.10
Purchase #7	$187.93	10.588%	$207.828	$207.83	$207.85	$207.80
7 purchase totals =	$1,019.83		$1,100.8757	$1,100.87	$1,100.95	$1,100.90