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	$194.55	12.260%	$218.4018	$218.40	$218.40	$218.40
Purchase #2	$187.38	5.626%	$197.922	$197.92	$197.90	$197.90
Purchase #3	$50.92	3.239%	$52.5693	$52.57	$52.55	$52.60
Purchase #4	$172.48	4.399%	$180.0674	$180.07	$180.05	$180.10
Purchase #5	$48.84	12.459%	$54.925	$54.93	$54.95	$54.90
Purchase #6	$34.98	7.445%	$37.5843	$37.58	$37.60	$37.60
Purchase #7	$22.45	13.418%	$25.4623	$25.46	$25.45	$25.50
7 purchase totals =	$711.60		$766.9321	$766.93	$766.90	$767.00