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	$48.30	8.451%	$52.3818	$52.38	$52.40	$52.40
Purchase #2	$19.27	13.360%	$21.8445	$21.84	$21.85	$21.80
Purchase #3	$125.72	3.437%	$130.041	$130.04	$130.05	$130.00
Purchase #4	$101.97	10.466%	$112.6422	$112.64	$112.65	$112.60
Purchase #5	$235.26	10.369%	$259.6541	$259.65	$259.65	$259.70
Purchase #6	$26.88	7.392%	$28.867	$28.87	$28.85	$28.90
Purchase #7	$98.56	13.108%	$111.4792	$111.48	$111.50	$111.50
7 purchase totals =	$655.96		$716.9098	$716.90	$716.95	$716.90