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	$140.42	11.768%	$156.9446	$156.94	$156.95	$156.90
Purchase #2	$129.72	11.860%	$145.1048	$145.10	$145.10	$145.10
Purchase #3	$155.27	11.831%	$173.64	$173.64	$173.65	$173.60
Purchase #4	$28.34	12.316%	$31.8304	$31.83	$31.85	$31.80
Purchase #5	$93.70	5.228%	$98.5986	$98.60	$98.60	$98.60
Purchase #6	$69.73	12.734%	$78.6094	$78.61	$78.60	$78.60
Purchase #7	$137.63	11.847%	$153.935	$153.94	$153.95	$153.90
7 purchase totals =	$754.81		$838.6628	$838.66	$838.70	$838.50