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	$74.64	3.279%	$77.0874	$77.09	$77.10	$77.10
Purchase #2	$49.50	10.173%	$54.5356	$54.54	$54.55	$54.50
Purchase #3	$33.94	3.437%	$35.1065	$35.11	$35.10	$35.10
Purchase #4	$114.69	11.357%	$127.7153	$127.72	$127.70	$127.70
Purchase #5	$10.28	6.341%	$10.9319	$10.93	$10.95	$10.90
Purchase #6	$109.81	8.219%	$118.8353	$118.84	$118.85	$118.80
Purchase #7	$9.89	5.835%	$10.4671	$10.47	$10.45	$10.50
7 purchase totals =	$402.75		$434.6791	$434.70	$434.70	$434.60