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	$219.65	11.725%	$245.404	$245.40	$245.40	$245.40
Purchase #2	$179.95	6.588%	$191.8051	$191.81	$191.80	$191.80
Purchase #3	$77.44	13.743%	$88.0826	$88.08	$88.10	$88.10
Purchase #4	$128.86	11.179%	$143.2653	$143.27	$143.25	$143.30
Purchase #5	$122.99	13.556%	$139.6625	$139.66	$139.65	$139.70
Purchase #6	$212.92	4.553%	$222.6142	$222.61	$222.60	$222.60
Purchase #7	$135.55	4.153%	$141.1794	$141.18	$141.20	$141.20
7 purchase totals =	$1,077.36		$1,172.0131	$1,172.01	$1,172.00	$1,172.10