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	$231.40	9.409%	$253.1724	$253.17	$253.15	$253.20
Purchase #2	$101.94	11.112%	$113.2676	$113.27	$113.25	$113.30
Purchase #3	$35.82	5.617%	$37.832	$37.83	$37.85	$37.80
Purchase #4	$140.88	4.122%	$146.6871	$146.69	$146.70	$146.70
Purchase #5	$141.85	3.359%	$146.6147	$146.61	$146.60	$146.60
Purchase #6	$9.69	11.309%	$10.7858	$10.79	$10.80	$10.80
Purchase #7	$105.49	3.679%	$109.371	$109.37	$109.35	$109.40
7 purchase totals =	$767.07		$817.7306	$817.73	$817.70	$817.80