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	$106.42	6.686%	$113.5352	$113.54	$113.55	$113.50
Purchase #2	$179.69	6.157%	$190.7535	$190.75	$190.75	$190.80
Purchase #3	$184.50	3.469%	$190.9003	$190.90	$190.90	$190.90
Purchase #4	$89.45	3.118%	$92.2391	$92.24	$92.25	$92.20
Purchase #5	$144.60	3.844%	$150.1584	$150.16	$150.15	$150.20
Purchase #6	$125.56	13.451%	$142.4491	$142.45	$142.45	$142.40
Purchase #7	$105.35	9.244%	$115.0886	$115.09	$115.10	$115.10
7 purchase totals =	$935.57		$995.1242	$995.13	$995.15	$995.10