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	$86.38	9.282%	$94.3978	$94.40	$94.40	$94.40
Purchase #2	$146.90	10.354%	$162.11	$162.11	$162.10	$162.10
Purchase #3	$232.82	5.705%	$246.1024	$246.10	$246.10	$246.10
Purchase #4	$146.70	8.127%	$158.6223	$158.62	$158.60	$158.60
Purchase #5	$70.68	11.445%	$78.7693	$78.77	$78.75	$78.80
Purchase #6	$237.59	4.873%	$249.1678	$249.17	$249.15	$249.20
Purchase #7	$138.43	4.244%	$144.305	$144.31	$144.30	$144.30
7 purchase totals =	$1,059.50		$1,133.4746	$1,133.48	$1,133.40	$1,133.50