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	$118.98	6.858%	$127.1396	$127.14	$127.15	$127.10
Purchase #2	$78.84	8.729%	$85.7219	$85.72	$85.70	$85.70
Purchase #3	$95.42	9.555%	$104.5374	$104.54	$104.55	$104.50
Purchase #4	$69.57	3.600%	$72.0745	$72.07	$72.05	$72.10
Purchase #5	$65.91	9.272%	$72.0212	$72.02	$72.00	$72.00
Purchase #6	$228.57	10.868%	$253.411	$253.41	$253.40	$253.40
Purchase #7	$106.85	4.608%	$111.7736	$111.77	$111.75	$111.80
7 purchase totals =	$764.14		$826.6792	$826.67	$826.60	$826.60