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	$148.38	11.302%	$165.1499	$165.15	$165.15	$165.10
Purchase #2	$227.43	6.308%	$241.7763	$241.78	$241.80	$241.80
Purchase #3	$60.31	8.758%	$65.5919	$65.59	$65.60	$65.60
Purchase #4	$151.54	11.369%	$168.7686	$168.77	$168.75	$168.80
Purchase #5	$96.99	3.692%	$100.5709	$100.57	$100.55	$100.60
Purchase #6	$184.99	4.833%	$193.9306	$193.93	$193.95	$193.90
Purchase #7	$71.37	7.540%	$76.7513	$76.75	$76.75	$76.80
7 purchase totals =	$941.01		$1,012.5395	$1,012.54	$1,012.55	$1,012.60