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	$159.70	12.591%	$179.8078	$179.81	$179.80	$179.80
Purchase #2	$152.86	10.671%	$169.1717	$169.17	$169.15	$169.20
Purchase #3	$158.34	6.602%	$168.7936	$168.79	$168.80	$168.80
Purchase #4	$119.87	3.854%	$124.4898	$124.49	$124.50	$124.50
Purchase #5	$48.60	13.295%	$55.0614	$55.06	$55.05	$55.10
Purchase #6	$57.27	3.167%	$59.0837	$59.08	$59.10	$59.10
Purchase #7	$169.73	13.467%	$192.5875	$192.59	$192.60	$192.60
7 purchase totals =	$866.37		$948.9955	$948.99	$949.00	$949.10