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	$247.83	13.721%	$281.8348	$281.83	$281.85	$281.80
Purchase #2	$86.88	6.181%	$92.2501	$92.25	$92.25	$92.30
Purchase #3	$178.61	8.532%	$193.849	$193.85	$193.85	$193.80
Purchase #4	$50.84	6.153%	$53.9682	$53.97	$53.95	$54.00
Purchase #5	$149.40	12.724%	$168.4097	$168.41	$168.40	$168.40
Purchase #6	$141.61	7.745%	$152.5777	$152.58	$152.60	$152.60
Purchase #7	$199.48	5.280%	$210.0125	$210.01	$210.00	$210.00
7 purchase totals =	$1,054.65		$1,152.9020	$1,152.90	$1,152.90	$1,152.90