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	$15.96	9.203%	$17.4288	$17.43	$17.45	$17.40
Purchase #2	$163.59	4.849%	$171.5225	$171.52	$171.50	$171.50
Purchase #3	$87.57	3.655%	$90.7707	$90.77	$90.75	$90.80
Purchase #4	$229.44	3.806%	$238.1725	$238.17	$238.15	$238.20
Purchase #5	$144.99	7.779%	$156.2688	$156.27	$156.25	$156.30
Purchase #6	$123.29	5.830%	$130.4778	$130.48	$130.50	$130.50
Purchase #7	$199.78	9.104%	$217.968	$217.97	$217.95	$218.00
7 purchase totals =	$964.62		$1,022.6091	$1,022.61	$1,022.55	$1,022.70