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	$140.52	13.850%	$159.982	$159.98	$160.00	$160.00
Purchase #2	$67.99	12.342%	$76.3813	$76.38	$76.40	$76.40
Purchase #3	$151.31	13.482%	$171.7096	$171.71	$171.70	$171.70
Purchase #4	$187.39	8.346%	$203.0296	$203.03	$203.05	$203.00
Purchase #5	$43.77	3.139%	$45.1439	$45.14	$45.15	$45.10
Purchase #6	$52.55	8.634%	$57.0872	$57.09	$57.10	$57.10
Purchase #7	$82.27	10.431%	$90.8516	$90.85	$90.85	$90.90
7 purchase totals =	$725.80		$804.1852	$804.18	$804.25	$804.20