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	$66.49	7.130%	$71.2307	$71.23	$71.25	$71.20
Purchase #2	$242.75	11.762%	$271.3023	$271.30	$271.30	$271.30
Purchase #3	$65.59	9.171%	$71.6053	$71.61	$71.60	$71.60
Purchase #4	$127.27	13.599%	$144.5774	$144.58	$144.60	$144.60
Purchase #5	$76.78	11.288%	$85.4469	$85.45	$85.45	$85.40
Purchase #6	$37.95	13.239%	$42.9742	$42.97	$42.95	$43.00
Purchase #7	$34.59	4.633%	$36.1926	$36.19	$36.20	$36.20
7 purchase totals =	$651.42		$723.3294	$723.33	$723.35	$723.30