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	$162.69	7.584%	$175.0284	$175.03	$175.05	$175.00
Purchase #2	$91.95	8.864%	$100.1004	$100.10	$100.10	$100.10
Purchase #3	$165.80	4.625%	$173.4683	$173.47	$173.45	$173.50
Purchase #4	$105.59	10.571%	$116.7519	$116.75	$116.75	$116.80
Purchase #5	$33.25	6.193%	$35.3092	$35.31	$35.30	$35.30
Purchase #6	$112.53	12.746%	$126.8731	$126.87	$126.85	$126.90
Purchase #7	$123.66	3.750%	$128.2973	$128.30	$128.30	$128.30
7 purchase totals =	$795.47		$855.8286	$855.83	$855.80	$855.90