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	$215.37	6.441%	$229.242	$229.24	$229.25	$229.20
Purchase #2	$9.69	12.557%	$10.9068	$10.91	$10.90	$10.90
Purchase #3	$199.72	12.284%	$224.2536	$224.25	$224.25	$224.30
Purchase #4	$125.70	13.657%	$142.8668	$142.87	$142.85	$142.90
Purchase #5	$234.32	6.502%	$249.5555	$249.56	$249.55	$249.60
Purchase #6	$18.83	12.406%	$21.166	$21.17	$21.15	$21.20
Purchase #7	$175.81	6.162%	$186.6434	$186.64	$186.65	$186.60
7 purchase totals =	$979.44		$1,064.6341	$1,064.64	$1,064.60	$1,064.70