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	$44.89	5.704%	$47.4505	$47.45	$47.45	$47.50
Purchase #2	$97.28	3.423%	$100.6099	$100.61	$100.60	$100.60
Purchase #3	$12.28	9.474%	$13.4434	$13.44	$13.45	$13.40
Purchase #4	$60.86	7.761%	$65.5833	$65.58	$65.60	$65.60
Purchase #5	$184.62	10.414%	$203.8463	$203.85	$203.85	$203.80
Purchase #6	$141.31	6.861%	$151.0053	$151.01	$151.00	$151.00
Purchase #7	$194.30	12.207%	$218.0182	$218.02	$218.00	$218.00
7 purchase totals =	$735.54		$799.9569	$799.96	$799.95	$799.90