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	$109.27	6.758%	$116.6545	$116.65	$116.65	$116.70
Purchase #2	$227.65	7.572%	$244.8877	$244.89	$244.90	$244.90
Purchase #3	$130.94	4.284%	$136.5495	$136.55	$136.55	$136.50
Purchase #4	$149.31	6.603%	$159.1689	$159.17	$159.15	$159.20
Purchase #5	$9.45	3.410%	$9.7722	$9.77	$9.75	$9.80
Purchase #6	$126.38	4.376%	$131.9104	$131.91	$131.90	$131.90
Purchase #7	$225.84	13.540%	$256.4187	$256.42	$256.40	$256.40
7 purchase totals =	$978.84		$1,055.3619	$1,055.36	$1,055.30	$1,055.40