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	$92.26	4.509%	$96.42	$96.42	$96.40	$96.40
Purchase #2	$229.55	11.193%	$255.2435	$255.24	$255.25	$255.20
Purchase #3	$157.92	6.669%	$168.4517	$168.45	$168.45	$168.50
Purchase #4	$57.30	3.129%	$59.0929	$59.09	$59.10	$59.10
Purchase #5	$154.33	10.644%	$170.7569	$170.76	$170.75	$170.80
Purchase #6	$210.87	12.796%	$237.8529	$237.85	$237.85	$237.90
Purchase #7	$123.44	5.843%	$130.6526	$130.65	$130.65	$130.70
7 purchase totals =	$1,025.67		$1,118.4705	$1,118.46	$1,118.45	$1,118.60