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	$120.82	11.673%	$134.9233	$134.92	$134.90	$134.90
Purchase #2	$148.72	9.241%	$162.4632	$162.46	$162.45	$162.50
Purchase #3	$249.60	5.210%	$262.6042	$262.60	$262.60	$262.60
Purchase #4	$55.50	8.821%	$60.3957	$60.40	$60.40	$60.40
Purchase #5	$196.36	6.495%	$209.1136	$209.11	$209.10	$209.10
Purchase #6	$46.59	3.160%	$48.0622	$48.06	$48.05	$48.10
Purchase #7	$153.32	4.744%	$160.5935	$160.59	$160.60	$160.60
7 purchase totals =	$970.91		$1,038.1557	$1,038.14	$1,038.10	$1,038.20