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	$163.83	6.507%	$174.4904	$174.49	$174.50	$174.50
Purchase #2	$17.97	3.721%	$18.6387	$18.64	$18.65	$18.60
Purchase #3	$112.30	13.340%	$127.2808	$127.28	$127.30	$127.30
Purchase #4	$118.55	5.505%	$125.0762	$125.08	$125.10	$125.10
Purchase #5	$190.50	13.792%	$216.7738	$216.77	$216.75	$216.80
Purchase #6	$49.42	9.472%	$54.1011	$54.10	$54.10	$54.10
Purchase #7	$41.33	10.311%	$45.5915	$45.59	$45.60	$45.60
7 purchase totals =	$693.90		$761.9525	$761.95	$762.00	$762.00