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	$68.74	4.855%	$72.0773	$72.08	$72.10	$72.10
Purchase #2	$71.69	9.519%	$78.5142	$78.51	$78.50	$78.50
Purchase #3	$151.83	13.564%	$172.4242	$172.42	$172.40	$172.40
Purchase #4	$237.78	3.440%	$245.9596	$245.96	$245.95	$246.00
Purchase #5	$242.99	6.483%	$258.743	$258.74	$258.75	$258.70
Purchase #6	$20.56	10.611%	$22.7416	$22.74	$22.75	$22.70
Purchase #7	$228.85	3.691%	$237.2969	$237.30	$237.30	$237.30
7 purchase totals =	$1,022.44		$1,087.7568	$1,087.75	$1,087.75	$1,087.70