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	$146.69	9.259%	$160.272	$160.27	$160.25	$160.30
Purchase #2	$144.80	9.709%	$158.8586	$158.86	$158.85	$158.90
Purchase #3	$68.84	13.794%	$78.3358	$78.34	$78.35	$78.30
Purchase #4	$74.41	8.257%	$80.554	$80.55	$80.55	$80.60
Purchase #5	$57.51	4.303%	$59.9847	$59.98	$60.00	$60.00
Purchase #6	$140.59	8.397%	$152.3953	$152.40	$152.40	$152.40
Purchase #7	$239.37	5.647%	$252.8872	$252.89	$252.90	$252.90
7 purchase totals =	$872.21		$943.2876	$943.29	$943.30	$943.40