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	$63.83	6.439%	$67.94	$67.94	$67.95	$67.90
Purchase #2	$194.25	3.126%	$200.3223	$200.32	$200.30	$200.30
Purchase #3	$47.32	12.207%	$53.0964	$53.10	$53.10	$53.10
Purchase #4	$104.94	13.767%	$119.3871	$119.39	$119.40	$119.40
Purchase #5	$43.96	12.714%	$49.5491	$49.55	$49.55	$49.50
Purchase #6	$92.34	9.232%	$100.8648	$100.86	$100.85	$100.90
Purchase #7	$54.93	7.147%	$58.8558	$58.86	$58.85	$58.90
7 purchase totals =	$601.57		$650.0155	$650.02	$650.00	$650.00