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	$145.31	12.581%	$163.5915	$163.59	$163.60	$163.60
Purchase #2	$184.91	6.328%	$196.6111	$196.61	$196.60	$196.60
Purchase #3	$170.63	10.474%	$188.5018	$188.50	$188.50	$188.50
Purchase #4	$134.96	13.763%	$153.5345	$153.53	$153.55	$153.50
Purchase #5	$41.28	9.355%	$45.1417	$45.14	$45.15	$45.10
Purchase #6	$60.83	11.508%	$67.8303	$67.83	$67.85	$67.80
Purchase #7	$210.74	10.599%	$233.0763	$233.08	$233.10	$233.10
7 purchase totals =	$948.66		$1,048.2872	$1,048.28	$1,048.35	$1,048.20