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	$184.38	13.625%	$209.5018	$209.50	$209.50	$209.50
Purchase #2	$45.35	13.257%	$51.362	$51.36	$51.35	$51.40
Purchase #3	$234.41	12.462%	$263.6222	$263.62	$263.60	$263.60
Purchase #4	$229.27	8.680%	$249.1706	$249.17	$249.15	$249.20
Purchase #5	$142.71	11.147%	$158.6179	$158.62	$158.60	$158.60
Purchase #6	$63.42	13.235%	$71.8136	$71.81	$71.80	$71.80
Purchase #7	$38.58	12.380%	$43.3562	$43.36	$43.35	$43.40
7 purchase totals =	$938.12		$1,047.4443	$1,047.44	$1,047.35	$1,047.50