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	$77.52	9.130%	$84.5976	$84.60	$84.60	$84.60
Purchase #2	$95.28	9.569%	$104.3973	$104.40	$104.40	$104.40
Purchase #3	$104.52	9.546%	$114.4975	$114.50	$114.50	$114.50
Purchase #4	$85.90	4.113%	$89.4331	$89.43	$89.45	$89.40
Purchase #5	$136.91	4.364%	$142.8848	$142.88	$142.90	$142.90
Purchase #6	$161.95	6.801%	$172.9642	$172.96	$172.95	$173.00
Purchase #7	$192.64	4.168%	$200.6692	$200.67	$200.65	$200.70
7 purchase totals =	$854.72		$909.4437	$909.44	$909.45	$909.50