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	$243.87	9.365%	$266.7084	$266.71	$266.70	$266.70
Purchase #2	$169.47	13.374%	$192.1349	$192.13	$192.15	$192.10
Purchase #3	$14.44	9.588%	$15.8245	$15.82	$15.80	$15.80
Purchase #4	$164.48	9.379%	$179.9066	$179.91	$179.90	$179.90
Purchase #5	$99.25	6.483%	$105.6844	$105.68	$105.70	$105.70
Purchase #6	$193.85	12.612%	$218.2984	$218.30	$218.30	$218.30
Purchase #7	$79.31	4.548%	$82.917	$82.92	$82.90	$82.90
7 purchase totals =	$964.67		$1,061.4742	$1,061.47	$1,061.45	$1,061.40