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	$59.62	13.366%	$67.5888	$67.59	$67.60	$67.60
Purchase #2	$71.69	8.821%	$78.0138	$78.01	$78.00	$78.00
Purchase #3	$14.89	7.708%	$16.0377	$16.04	$16.05	$16.00
Purchase #4	$192.30	13.613%	$218.4778	$218.48	$218.50	$218.50
Purchase #5	$90.74	4.278%	$94.6219	$94.62	$94.60	$94.60
Purchase #6	$174.65	9.259%	$190.8208	$190.82	$190.80	$190.80
Purchase #7	$48.39	4.103%	$50.3754	$50.38	$50.40	$50.40
7 purchase totals =	$652.28		$715.9362	$715.94	$715.95	$715.90