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	$144.51	4.755%	$151.3815	$151.38	$151.40	$151.40
Purchase #2	$89.40	6.189%	$94.933	$94.93	$94.95	$94.90
Purchase #3	$183.32	5.694%	$193.7582	$193.76	$193.75	$193.80
Purchase #4	$52.67	13.127%	$59.584	$59.58	$59.60	$59.60
Purchase #5	$166.60	4.748%	$174.5102	$174.51	$174.50	$174.50
Purchase #6	$214.90	12.305%	$241.3434	$241.34	$241.35	$241.30
Purchase #7	$152.33	6.188%	$161.7562	$161.76	$161.75	$161.80
7 purchase totals =	$1,003.73		$1,077.2665	$1,077.26	$1,077.30	$1,077.30