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	$60.83	11.673%	$67.9307	$67.93	$67.95	$67.90
Purchase #2	$128.60	12.712%	$144.9476	$144.95	$144.95	$144.90
Purchase #3	$171.95	10.312%	$189.6815	$189.68	$189.70	$189.70
Purchase #4	$116.44	4.495%	$121.674	$121.67	$121.65	$121.70
Purchase #5	$85.80	4.647%	$89.7871	$89.79	$89.80	$89.80
Purchase #6	$210.69	13.240%	$238.5854	$238.59	$238.60	$238.60
Purchase #7	$196.99	5.827%	$208.4686	$208.47	$208.45	$208.50
7 purchase totals =	$971.30		$1,061.0749	$1,061.08	$1,061.10	$1,061.10