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	$231.94	8.596%	$251.8776	$251.88	$251.90	$251.90
Purchase #2	$145.82	11.360%	$162.3852	$162.39	$162.40	$162.40
Purchase #3	$178.81	11.531%	$199.4286	$199.43	$199.45	$199.40
Purchase #4	$201.90	11.831%	$225.7868	$225.79	$225.80	$225.80
Purchase #5	$75.94	6.390%	$80.7926	$80.79	$80.80	$80.80
Purchase #6	$132.61	9.684%	$145.452	$145.45	$145.45	$145.50
Purchase #7	$114.41	11.112%	$127.1232	$127.12	$127.10	$127.10
7 purchase totals =	$1,081.43		$1,192.8460	$1,192.85	$1,192.90	$1,192.90