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	$151.69	7.636%	$163.273	$163.27	$163.25	$163.30
Purchase #2	$203.69	9.418%	$222.8735	$222.87	$222.85	$222.90
Purchase #3	$176.62	11.152%	$196.3167	$196.32	$196.30	$196.30
Purchase #4	$176.92	3.298%	$182.7548	$182.75	$182.75	$182.80
Purchase #5	$94.77	6.285%	$100.7263	$100.73	$100.75	$100.70
Purchase #6	$95.70	11.822%	$107.0137	$107.01	$107.00	$107.00
Purchase #7	$92.82	6.647%	$98.9897	$98.99	$99.00	$99.00
7 purchase totals =	$992.21		$1,071.9477	$1,071.94	$1,071.90	$1,072.00