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	$82.37	11.312%	$91.6877	$91.69	$91.70	$91.70
Purchase #2	$81.46	7.330%	$87.431	$87.43	$87.45	$87.40
Purchase #3	$53.60	5.491%	$56.5432	$56.54	$56.55	$56.50
Purchase #4	$250.73	11.578%	$279.7595	$279.76	$279.75	$279.80
Purchase #5	$153.62	10.431%	$169.6441	$169.64	$169.65	$169.60
Purchase #6	$205.76	5.766%	$217.6241	$217.62	$217.60	$217.60
Purchase #7	$92.95	6.560%	$99.0475	$99.05	$99.05	$99.00
7 purchase totals =	$920.49		$1,001.7371	$1,001.73	$1,001.75	$1,001.60