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	$97.83	3.407%	$101.1631	$101.16	$101.15	$101.20
Purchase #2	$92.69	7.830%	$99.9476	$99.95	$99.95	$99.90
Purchase #3	$184.87	8.558%	$200.6912	$200.69	$200.70	$200.70
Purchase #4	$145.31	13.435%	$164.8324	$164.83	$164.85	$164.80
Purchase #5	$93.86	6.133%	$99.6164	$99.62	$99.60	$99.60
Purchase #6	$171.70	10.586%	$189.8762	$189.88	$189.90	$189.90
Purchase #7	$166.45	3.686%	$172.5853	$172.59	$172.60	$172.60
7 purchase totals =	$952.71		$1,028.7122	$1,028.72	$1,028.75	$1,028.70