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	$106.43	6.578%	$113.431	$113.43	$113.45	$113.40
Purchase #2	$242.34	13.509%	$275.0777	$275.08	$275.10	$275.10
Purchase #3	$161.82	6.567%	$172.4467	$172.45	$172.45	$172.40
Purchase #4	$89.67	6.158%	$95.1919	$95.19	$95.20	$95.20
Purchase #5	$227.47	12.179%	$255.1736	$255.17	$255.15	$255.20
Purchase #6	$113.63	7.793%	$122.4852	$122.49	$122.50	$122.50
Purchase #7	$85.89	12.571%	$96.6872	$96.69	$96.70	$96.70
7 purchase totals =	$1,027.25		$1,130.4933	$1,130.50	$1,130.55	$1,130.50