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	$89.71	12.676%	$101.0816	$101.08	$101.10	$101.10
Purchase #2	$198.37	3.776%	$205.8605	$205.86	$205.85	$205.90
Purchase #3	$135.27	7.807%	$145.8305	$145.83	$145.85	$145.80
Purchase #4	$226.87	4.730%	$237.601	$237.60	$237.60	$237.60
Purchase #5	$179.93	5.291%	$189.4501	$189.45	$189.45	$189.50
Purchase #6	$221.46	5.731%	$234.1519	$234.15	$234.15	$234.20
Purchase #7	$12.69	8.407%	$13.7568	$13.76	$13.75	$13.80
7 purchase totals =	$1,064.30		$1,127.7324	$1,127.73	$1,127.75	$1,127.90