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	$60.67	10.572%	$67.084	$67.08	$67.10	$67.10
Purchase #2	$154.61	4.440%	$161.4747	$161.47	$161.45	$161.50
Purchase #3	$167.27	9.728%	$183.542	$183.54	$183.55	$183.50
Purchase #4	$33.93	3.846%	$35.2349	$35.23	$35.25	$35.20
Purchase #5	$171.35	5.267%	$180.375	$180.38	$180.40	$180.40
Purchase #6	$64.38	4.233%	$67.1052	$67.11	$67.10	$67.10
Purchase #7	$14.62	7.108%	$15.6592	$15.66	$15.65	$15.70
7 purchase totals =	$666.83		$710.4750	$710.47	$710.50	$710.50