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	$67.70	13.619%	$76.9201	$76.92	$76.90	$76.90
Purchase #2	$193.85	11.720%	$216.5692	$216.57	$216.55	$216.60
Purchase #3	$237.63	7.651%	$255.8111	$255.81	$255.80	$255.80
Purchase #4	$126.83	8.296%	$137.3518	$137.35	$137.35	$137.40
Purchase #5	$93.47	7.263%	$100.2587	$100.26	$100.25	$100.30
Purchase #6	$65.44	8.584%	$71.0574	$71.06	$71.05	$71.10
Purchase #7	$204.60	3.560%	$211.8838	$211.88	$211.90	$211.90
7 purchase totals =	$989.52		$1,069.8521	$1,069.85	$1,069.80	$1,070.00