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	$32.54	3.519%	$33.6851	$33.69	$33.70	$33.70
Purchase #2	$164.86	9.249%	$180.1079	$180.11	$180.10	$180.10
Purchase #3	$165.75	12.500%	$186.4688	$186.47	$186.45	$186.50
Purchase #4	$57.42	6.253%	$61.0105	$61.01	$61.00	$61.00
Purchase #5	$128.92	13.694%	$146.5743	$146.57	$146.55	$146.60
Purchase #6	$55.59	12.339%	$62.4493	$62.45	$62.45	$62.40
Purchase #7	$33.50	5.491%	$35.3395	$35.34	$35.35	$35.30
7 purchase totals =	$638.58		$705.6354	$705.64	$705.60	$705.60