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	$94.28	6.144%	$100.0726	$100.07	$100.05	$100.10
Purchase #2	$111.27	13.294%	$126.0622	$126.06	$126.05	$126.10
Purchase #3	$194.97	12.781%	$219.8891	$219.89	$219.90	$219.90
Purchase #4	$128.38	3.178%	$132.4599	$132.46	$132.45	$132.50
Purchase #5	$51.56	11.235%	$57.3528	$57.35	$57.35	$57.40
Purchase #6	$85.65	7.638%	$92.1919	$92.19	$92.20	$92.20
Purchase #7	$49.91	8.813%	$54.3086	$54.31	$54.30	$54.30
7 purchase totals =	$716.02		$782.3371	$782.33	$782.30	$782.50