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	$64.38	12.570%	$72.4726	$72.47	$72.45	$72.50
Purchase #2	$85.87	13.833%	$97.7484	$97.75	$97.75	$97.70
Purchase #3	$173.85	4.606%	$181.8575	$181.86	$181.85	$181.90
Purchase #4	$131.31	9.607%	$143.925	$143.93	$143.95	$143.90
Purchase #5	$9.48	7.450%	$10.1863	$10.19	$10.20	$10.20
Purchase #6	$244.52	9.397%	$267.4975	$267.50	$267.50	$267.50
Purchase #7	$214.60	13.123%	$242.762	$242.76	$242.75	$242.80
7 purchase totals =	$924.01		$1,016.4493	$1,016.46	$1,016.45	$1,016.50