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	$165.29	6.191%	$175.5231	$175.52	$175.50	$175.50
Purchase #2	$75.28	7.395%	$80.847	$80.85	$80.85	$80.80
Purchase #3	$114.76	11.120%	$127.5213	$127.52	$127.50	$127.50
Purchase #4	$248.42	10.353%	$274.1389	$274.14	$274.15	$274.10
Purchase #5	$89.85	6.273%	$95.4863	$95.49	$95.50	$95.50
Purchase #6	$199.29	11.537%	$222.2821	$222.28	$222.30	$222.30
Purchase #7	$132.61	5.690%	$140.1555	$140.16	$140.15	$140.20
7 purchase totals =	$1,025.50		$1,115.9542	$1,115.96	$1,115.95	$1,115.90