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	$49.35	8.749%	$53.6676	$53.67	$53.65	$53.70
Purchase #2	$243.75	10.666%	$269.7484	$269.75	$269.75	$269.70
Purchase #3	$241.72	3.631%	$250.4969	$250.50	$250.50	$250.50
Purchase #4	$107.41	9.791%	$117.9265	$117.93	$117.95	$117.90
Purchase #5	$82.59	7.803%	$89.0345	$89.03	$89.05	$89.00
Purchase #6	$68.82	3.189%	$71.0147	$71.01	$71.00	$71.00
Purchase #7	$146.45	11.111%	$162.7221	$162.72	$162.70	$162.70
7 purchase totals =	$940.09		$1,014.6107	$1,014.61	$1,014.60	$1,014.50