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	$58.85	11.167%	$65.4218	$65.42	$65.40	$65.40
Purchase #2	$20.58	13.164%	$23.2892	$23.29	$23.30	$23.30
Purchase #3	$6.41	11.605%	$7.1539	$7.15	$7.15	$7.20
Purchase #4	$80.86	11.712%	$90.3303	$90.33	$90.35	$90.30
Purchase #5	$172.78	9.822%	$189.7505	$189.75	$189.75	$189.80
Purchase #6	$40.47	11.817%	$45.2523	$45.25	$45.25	$45.30
Purchase #7	$66.94	11.432%	$74.5926	$74.59	$74.60	$74.60
7 purchase totals =	$446.89		$495.7906	$495.78	$495.80	$495.90