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	$148.30	8.182%	$160.4339	$160.43	$160.45	$160.40
Purchase #2	$242.97	13.745%	$276.3662	$276.37	$276.35	$276.40
Purchase #3	$198.66	5.866%	$210.3134	$210.31	$210.30	$210.30
Purchase #4	$123.61	4.599%	$129.2948	$129.29	$129.30	$129.30
Purchase #5	$78.90	13.793%	$89.7827	$89.78	$89.80	$89.80
Purchase #6	$206.38	7.701%	$222.2733	$222.27	$222.25	$222.30
Purchase #7	$46.55	10.712%	$51.5364	$51.54	$51.55	$51.50
7 purchase totals =	$1,045.37		$1,140.0007	$1,139.99	$1,140.00	$1,140.00