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	$185.74	3.797%	$192.7925	$192.79	$192.80	$192.80
Purchase #2	$86.89	6.115%	$92.2033	$92.20	$92.20	$92.20
Purchase #3	$99.82	4.748%	$104.5595	$104.56	$104.55	$104.60
Purchase #4	$217.62	13.818%	$247.6907	$247.69	$247.70	$247.70
Purchase #5	$160.38	5.295%	$168.8721	$168.87	$168.85	$168.90
Purchase #6	$132.85	8.765%	$144.4943	$144.49	$144.50	$144.50
Purchase #7	$50.55	7.366%	$54.2735	$54.27	$54.25	$54.30
7 purchase totals =	$933.85		$1,004.8859	$1,004.87	$1,004.85	$1,005.00