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	$126.77	3.837%	$131.6342	$131.63	$131.65	$131.60
Purchase #2	$181.42	10.420%	$200.324	$200.32	$200.30	$200.30
Purchase #3	$19.61	12.835%	$22.1269	$22.13	$22.15	$22.10
Purchase #4	$43.47	12.407%	$48.8633	$48.86	$48.85	$48.90
Purchase #5	$154.94	8.231%	$167.6931	$167.69	$167.70	$167.70
Purchase #6	$56.30	3.794%	$58.436	$58.44	$58.45	$58.40
Purchase #7	$158.83	8.641%	$172.5545	$172.55	$172.55	$172.60
7 purchase totals =	$741.34		$801.6320	$801.62	$801.65	$801.60