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	$67.69	4.739%	$70.8978	$70.90	$70.90	$70.90
Purchase #2	$114.67	13.604%	$130.2697	$130.27	$130.25	$130.30
Purchase #3	$46.43	4.391%	$48.4687	$48.47	$48.45	$48.50
Purchase #4	$200.90	5.542%	$212.0339	$212.03	$212.05	$212.00
Purchase #5	$20.91	3.556%	$21.6536	$21.65	$21.65	$21.70
Purchase #6	$41.35	6.221%	$43.9224	$43.92	$43.90	$43.90
Purchase #7	$85.50	8.446%	$92.7213	$92.72	$92.70	$92.70
7 purchase totals =	$577.45		$619.9674	$619.96	$619.90	$620.00