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	$165.39	10.370%	$182.5409	$182.54	$182.55	$182.50
Purchase #2	$117.98	10.166%	$129.9738	$129.97	$129.95	$130.00
Purchase #3	$235.87	6.116%	$250.2958	$250.30	$250.30	$250.30
Purchase #4	$208.93	4.150%	$217.6006	$217.60	$217.60	$217.60
Purchase #5	$22.82	7.757%	$24.5901	$24.59	$24.60	$24.60
Purchase #6	$74.91	3.583%	$77.594	$77.59	$77.60	$77.60
Purchase #7	$114.77	4.468%	$119.8979	$119.90	$119.90	$119.90
7 purchase totals =	$940.67		$1,002.4931	$1,002.49	$1,002.50	$1,002.50