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	$148.59	10.302%	$163.8977	$163.90	$163.90	$163.90
Purchase #2	$51.29	5.769%	$54.2489	$54.25	$54.25	$54.20
Purchase #3	$88.59	12.245%	$99.4378	$99.44	$99.45	$99.40
Purchase #4	$189.89	3.418%	$196.3804	$196.38	$196.40	$196.40
Purchase #5	$97.77	4.822%	$102.4845	$102.48	$102.50	$102.50
Purchase #6	$147.27	4.360%	$153.691	$153.69	$153.70	$153.70
Purchase #7	$8.97	12.727%	$10.1116	$10.11	$10.10	$10.10
7 purchase totals =	$732.37		$780.2519	$780.25	$780.30	$780.20