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	$122.71	7.136%	$131.4666	$131.47	$131.45	$131.50
Purchase #2	$163.69	13.550%	$185.87	$185.87	$185.85	$185.90
Purchase #3	$216.29	5.389%	$227.9459	$227.95	$227.95	$227.90
Purchase #4	$89.75	12.781%	$101.2209	$101.22	$101.20	$101.20
Purchase #5	$110.45	3.356%	$114.1567	$114.16	$114.15	$114.20
Purchase #6	$137.38	12.773%	$154.9275	$154.93	$154.95	$154.90
Purchase #7	$48.49	8.109%	$52.4221	$52.42	$52.40	$52.40
7 purchase totals =	$888.76		$968.0097	$968.02	$967.95	$968.00