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	$59.49	4.635%	$62.2474	$62.25	$62.25	$62.20
Purchase #2	$133.38	13.247%	$151.0488	$151.05	$151.05	$151.00
Purchase #3	$38.58	7.353%	$41.4168	$41.42	$41.40	$41.40
Purchase #4	$38.30	9.192%	$41.8205	$41.82	$41.80	$41.80
Purchase #5	$218.26	13.844%	$248.4759	$248.48	$248.50	$248.50
Purchase #6	$92.50	11.403%	$103.0478	$103.05	$103.05	$103.00
Purchase #7	$71.90	6.354%	$76.4685	$76.47	$76.45	$76.50
7 purchase totals =	$652.41		$724.5257	$724.54	$724.50	$724.40