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	$92.27	4.528%	$96.448	$96.45	$96.45	$96.40
Purchase #2	$74.77	7.163%	$80.1258	$80.13	$80.15	$80.10
Purchase #3	$164.95	12.397%	$185.3989	$185.40	$185.40	$185.40
Purchase #4	$240.41	8.382%	$260.5612	$260.56	$260.55	$260.60
Purchase #5	$116.26	9.605%	$127.4268	$127.43	$127.45	$127.40
Purchase #6	$173.48	8.656%	$188.4964	$188.50	$188.50	$188.50
Purchase #7	$28.84	12.334%	$32.3971	$32.40	$32.40	$32.40
7 purchase totals =	$890.98		$970.8542	$970.87	$970.90	$970.80