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	$85.30	8.288%	$92.3697	$92.37	$92.35	$92.40
Purchase #2	$244.75	10.480%	$270.3998	$270.40	$270.40	$270.40
Purchase #3	$151.34	13.578%	$171.8889	$171.89	$171.90	$171.90
Purchase #4	$68.43	9.762%	$75.1101	$75.11	$75.10	$75.10
Purchase #5	$248.84	6.610%	$265.2883	$265.29	$265.30	$265.30
Purchase #6	$49.69	10.522%	$54.9184	$54.92	$54.90	$54.90
Purchase #7	$133.92	7.146%	$143.4899	$143.49	$143.50	$143.50
7 purchase totals =	$982.27		$1,073.4651	$1,073.47	$1,073.45	$1,073.50