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	$192.68	5.802%	$203.8593	$203.86	$203.85	$203.90
Purchase #2	$228.79	9.555%	$250.6509	$250.65	$250.65	$250.70
Purchase #3	$53.69	8.182%	$58.0829	$58.08	$58.10	$58.10
Purchase #4	$86.61	4.848%	$90.8089	$90.81	$90.80	$90.80
Purchase #5	$10.82	6.305%	$11.5022	$11.50	$11.50	$11.50
Purchase #6	$94.30	6.578%	$100.5031	$100.50	$100.50	$100.50
Purchase #7	$75.64	8.826%	$82.316	$82.32	$82.30	$82.30
7 purchase totals =	$742.53		$797.7233	$797.72	$797.70	$797.80