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	$56.49	9.349%	$61.7713	$61.77	$61.75	$61.80
Purchase #2	$135.91	11.189%	$151.117	$151.12	$151.10	$151.10
Purchase #3	$43.46	4.162%	$45.2688	$45.27	$45.25	$45.30
Purchase #4	$79.29	10.337%	$87.4862	$87.49	$87.50	$87.50
Purchase #5	$38.76	4.403%	$40.4666	$40.47	$40.45	$40.50
Purchase #6	$192.77	13.377%	$218.5568	$218.56	$218.55	$218.60
Purchase #7	$233.62	13.499%	$265.1564	$265.16	$265.15	$265.20
7 purchase totals =	$780.30		$869.8231	$869.84	$869.75	$870.00