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	$115.70	12.533%	$130.2007	$130.20	$130.20	$130.20
Purchase #2	$241.57	10.278%	$266.3986	$266.40	$266.40	$266.40
Purchase #3	$11.55	4.309%	$12.0477	$12.05	$12.05	$12.00
Purchase #4	$215.77	7.446%	$231.8362	$231.84	$231.85	$231.80
Purchase #5	$190.97	10.487%	$210.997	$211.00	$211.00	$211.00
Purchase #6	$74.78	12.191%	$83.8964	$83.90	$83.90	$83.90
Purchase #7	$173.64	13.127%	$196.4337	$196.43	$196.45	$196.40
7 purchase totals =	$1,023.98		$1,131.8103	$1,131.82	$1,131.85	$1,131.70