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	$103.79	10.519%	$114.7077	$114.71	$114.70	$114.70
Purchase #2	$190.66	3.136%	$196.6391	$196.64	$196.65	$196.60
Purchase #3	$145.31	12.147%	$162.9608	$162.96	$162.95	$163.00
Purchase #4	$89.47	10.208%	$98.6031	$98.60	$98.60	$98.60
Purchase #5	$59.86	11.383%	$66.6739	$66.67	$66.65	$66.70
Purchase #6	$76.27	13.269%	$86.3903	$86.39	$86.40	$86.40
Purchase #7	$88.61	5.321%	$93.3249	$93.32	$93.30	$93.30
7 purchase totals =	$753.97		$819.2998	$819.29	$819.25	$819.30