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	$92.83	8.450%	$100.6741	$100.67	$100.65	$100.70
Purchase #2	$162.63	3.504%	$168.3286	$168.33	$168.35	$168.30
Purchase #3	$223.94	6.231%	$237.8937	$237.89	$237.90	$237.90
Purchase #4	$173.71	7.420%	$186.5993	$186.60	$186.60	$186.60
Purchase #5	$24.99	11.496%	$27.8629	$27.86	$27.85	$27.90
Purchase #6	$154.68	3.391%	$159.9252	$159.93	$159.95	$159.90
Purchase #7	$48.38	8.746%	$52.6113	$52.61	$52.60	$52.60
7 purchase totals =	$881.16		$933.8951	$933.89	$933.90	$933.90