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	$144.36	12.587%	$162.5306	$162.53	$162.55	$162.50
Purchase #2	$30.68	11.688%	$34.2659	$34.27	$34.25	$34.30
Purchase #3	$56.54	5.860%	$59.8532	$59.85	$59.85	$59.90
Purchase #4	$57.59	4.595%	$60.2363	$60.24	$60.25	$60.20
Purchase #5	$90.97	8.843%	$99.0145	$99.01	$99.00	$99.00
Purchase #6	$164.40	5.481%	$173.4108	$173.41	$173.40	$173.40
Purchase #7	$222.70	4.715%	$233.2003	$233.20	$233.20	$233.20
7 purchase totals =	$767.24		$822.5116	$822.51	$822.50	$822.50