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	$240.51	10.337%	$265.3715	$265.37	$265.35	$265.40
Purchase #2	$19.64	11.217%	$21.843	$21.84	$21.85	$21.80
Purchase #3	$193.39	8.835%	$210.476	$210.48	$210.50	$210.50
Purchase #4	$137.99	13.568%	$156.7125	$156.71	$156.70	$156.70
Purchase #5	$233.40	6.456%	$248.4683	$248.47	$248.45	$248.50
Purchase #6	$100.91	7.747%	$108.7275	$108.73	$108.75	$108.70
Purchase #7	$56.95	5.111%	$59.8607	$59.86	$59.85	$59.90
7 purchase totals =	$982.79		$1,071.4595	$1,071.46	$1,071.45	$1,071.50