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	$154.82	6.302%	$164.5768	$164.58	$164.60	$164.60
Purchase #2	$137.66	6.202%	$146.1977	$146.20	$146.20	$146.20
Purchase #3	$63.45	5.413%	$66.8845	$66.88	$66.90	$66.90
Purchase #4	$31.47	7.351%	$33.7834	$33.78	$33.80	$33.80
Purchase #5	$66.29	12.316%	$74.4543	$74.45	$74.45	$74.50
Purchase #6	$11.82	8.726%	$12.8514	$12.85	$12.85	$12.90
Purchase #7	$239.96	10.351%	$264.7983	$264.80	$264.80	$264.80
7 purchase totals =	$705.47		$763.5464	$763.54	$763.60	$763.70