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	$158.48	3.249%	$163.629	$163.63	$163.65	$163.60
Purchase #2	$210.49	5.773%	$222.6416	$222.64	$222.65	$222.60
Purchase #3	$214.98	4.423%	$224.4886	$224.49	$224.50	$224.50
Purchase #4	$38.51	9.773%	$42.2736	$42.27	$42.25	$42.30
Purchase #5	$209.74	6.456%	$223.2808	$223.28	$223.30	$223.30
Purchase #6	$139.52	9.445%	$152.6977	$152.70	$152.70	$152.70
Purchase #7	$65.38	10.723%	$72.3907	$72.39	$72.40	$72.40
7 purchase totals =	$1,037.10		$1,101.4020	$1,101.40	$1,101.45	$1,101.40