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	$165.32	9.489%	$181.0072	$181.01	$181.00	$181.00
Purchase #2	$175.28	13.454%	$198.8622	$198.86	$198.85	$198.90
Purchase #3	$111.95	4.288%	$116.7504	$116.75	$116.75	$116.80
Purchase #4	$85.48	11.663%	$95.4495	$95.45	$95.45	$95.40
Purchase #5	$94.64	10.179%	$104.2734	$104.27	$104.25	$104.30
Purchase #6	$177.49	11.823%	$198.4746	$198.47	$198.45	$198.50
Purchase #7	$239.77	12.727%	$270.2855	$270.29	$270.30	$270.30
7 purchase totals =	$1,049.93		$1,165.1028	$1,165.10	$1,165.05	$1,165.20