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	$158.40	5.726%	$167.47	$167.47	$167.45	$167.50
Purchase #2	$198.71	6.784%	$212.1905	$212.19	$212.20	$212.20
Purchase #3	$176.76	9.516%	$193.5805	$193.58	$193.60	$193.60
Purchase #4	$41.42	13.248%	$46.9073	$46.91	$46.90	$46.90
Purchase #5	$17.30	8.254%	$18.7279	$18.73	$18.75	$18.70
Purchase #6	$71.73	9.694%	$78.6835	$78.68	$78.70	$78.70
Purchase #7	$64.47	3.661%	$66.8302	$66.83	$66.85	$66.80
7 purchase totals =	$728.79		$784.3899	$784.39	$784.45	$784.40