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	$58.90	11.510%	$65.6794	$65.68	$65.70	$65.70
Purchase #2	$134.58	9.502%	$147.3678	$147.37	$147.35	$147.40
Purchase #3	$213.95	11.600%	$238.7682	$238.77	$238.75	$238.80
Purchase #4	$233.88	6.859%	$249.9218	$249.92	$249.90	$249.90
Purchase #5	$204.30	7.335%	$219.2854	$219.29	$219.30	$219.30
Purchase #6	$112.65	9.541%	$123.3979	$123.40	$123.40	$123.40
Purchase #7	$48.81	11.290%	$54.3206	$54.32	$54.30	$54.30
7 purchase totals =	$1,007.07		$1,098.7411	$1,098.75	$1,098.70	$1,098.80