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	$191.92	12.352%	$215.626	$215.63	$215.65	$215.60
Purchase #2	$158.82	5.834%	$168.0856	$168.09	$168.10	$168.10
Purchase #3	$134.94	6.328%	$143.479	$143.48	$143.50	$143.50
Purchase #4	$93.84	12.110%	$105.204	$105.20	$105.20	$105.20
Purchase #5	$63.38	8.526%	$68.7838	$68.78	$68.80	$68.80
Purchase #6	$207.82	3.568%	$215.235	$215.24	$215.25	$215.20
Purchase #7	$127.56	13.270%	$144.4872	$144.49	$144.50	$144.50
7 purchase totals =	$978.28		$1,060.9006	$1,060.91	$1,061.00	$1,060.90