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	$240.80	6.165%	$255.6453	$255.65	$255.65	$255.60
Purchase #2	$241.98	7.138%	$259.2525	$259.25	$259.25	$259.30
Purchase #3	$133.72	13.599%	$151.9046	$151.90	$151.90	$151.90
Purchase #4	$91.40	3.826%	$94.897	$94.90	$94.90	$94.90
Purchase #5	$127.91	3.682%	$132.6196	$132.62	$132.60	$132.60
Purchase #6	$60.85	13.285%	$68.9339	$68.93	$68.95	$68.90
Purchase #7	$195.27	7.704%	$210.3136	$210.31	$210.30	$210.30
7 purchase totals =	$1,091.93		$1,173.5665	$1,173.56	$1,173.55	$1,173.50