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	$48.54	7.466%	$52.164	$52.16	$52.15	$52.20
Purchase #2	$239.90	8.262%	$259.7205	$259.72	$259.70	$259.70
Purchase #3	$91.51	7.133%	$98.0374	$98.04	$98.05	$98.00
Purchase #4	$51.36	6.835%	$54.8705	$54.87	$54.85	$54.90
Purchase #5	$131.78	13.462%	$149.5202	$149.52	$149.50	$149.50
Purchase #6	$85.84	7.708%	$92.4565	$92.46	$92.45	$92.50
Purchase #7	$196.86	13.113%	$222.6743	$222.67	$222.65	$222.70
7 purchase totals =	$845.79		$929.4434	$929.44	$929.35	$929.50