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	$163.38	6.564%	$174.1043	$174.10	$174.10	$174.10
Purchase #2	$38.54	7.211%	$41.3191	$41.32	$41.30	$41.30
Purchase #3	$157.93	9.390%	$172.7596	$172.76	$172.75	$172.80
Purchase #4	$159.90	13.732%	$181.8575	$181.86	$181.85	$181.90
Purchase #5	$99.85	8.856%	$108.6927	$108.69	$108.70	$108.70
Purchase #6	$61.37	10.491%	$67.8083	$67.81	$67.80	$67.80
Purchase #7	$201.57	10.261%	$222.2531	$222.25	$222.25	$222.30
7 purchase totals =	$882.54		$968.7946	$968.79	$968.75	$968.90