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	$250.87	4.252%	$261.537	$261.54	$261.55	$261.50
Purchase #2	$84.73	6.338%	$90.1002	$90.10	$90.10	$90.10
Purchase #3	$166.85	4.630%	$174.5752	$174.58	$174.60	$174.60
Purchase #4	$239.92	13.313%	$271.8605	$271.86	$271.85	$271.90
Purchase #5	$206.31	3.809%	$214.1683	$214.17	$214.15	$214.20
Purchase #6	$247.43	3.480%	$256.0406	$256.04	$256.05	$256.00
Purchase #7	$52.54	10.133%	$57.8639	$57.86	$57.85	$57.90
7 purchase totals =	$1,248.65		$1,326.1457	$1,326.15	$1,326.15	$1,326.20