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	$213.32	6.692%	$227.5954	$227.60	$227.60	$227.60
Purchase #2	$182.61	4.371%	$190.5919	$190.59	$190.60	$190.60
Purchase #3	$167.80	12.383%	$188.5787	$188.58	$188.60	$188.60
Purchase #4	$165.83	11.788%	$185.378	$185.38	$185.40	$185.40
Purchase #5	$152.80	3.265%	$157.7889	$157.79	$157.80	$157.80
Purchase #6	$30.71	7.466%	$33.0028	$33.00	$33.00	$33.00
Purchase #7	$32.96	5.662%	$34.8262	$34.83	$34.85	$34.80
7 purchase totals =	$946.03		$1,017.7619	$1,017.77	$1,017.85	$1,017.80