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	$200.44	6.619%	$213.7071	$213.71	$213.70	$213.70
Purchase #2	$56.98	6.291%	$60.5646	$60.56	$60.55	$60.60
Purchase #3	$152.97	12.494%	$172.0821	$172.08	$172.10	$172.10
Purchase #4	$187.77	4.745%	$196.6797	$196.68	$196.70	$196.70
Purchase #5	$68.94	13.392%	$78.1724	$78.17	$78.15	$78.20
Purchase #6	$199.72	9.734%	$219.1607	$219.16	$219.15	$219.20
Purchase #7	$19.91	9.829%	$21.867	$21.87	$21.85	$21.90
7 purchase totals =	$886.73		$962.2336	$962.23	$962.20	$962.40