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	$90.31	13.191%	$102.2228	$102.22	$102.20	$102.20
Purchase #2	$10.76	6.715%	$11.4825	$11.48	$11.50	$11.50
Purchase #3	$172.81	7.788%	$186.2684	$186.27	$186.25	$186.30
Purchase #4	$75.30	8.440%	$81.6553	$81.66	$81.65	$81.70
Purchase #5	$239.86	5.636%	$253.3785	$253.38	$253.40	$253.40
Purchase #6	$128.26	13.718%	$145.8547	$145.85	$145.85	$145.90
Purchase #7	$38.56	12.673%	$43.4467	$43.45	$43.45	$43.40
7 purchase totals =	$755.86		$824.3089	$824.31	$824.30	$824.40