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	$165.61	4.173%	$172.5209	$172.52	$172.50	$172.50
Purchase #2	$242.57	8.731%	$263.7488	$263.75	$263.75	$263.70
Purchase #3	$127.71	12.403%	$143.5499	$143.55	$143.55	$143.50
Purchase #4	$124.87	5.738%	$132.035	$132.04	$132.05	$132.00
Purchase #5	$151.46	12.155%	$169.87	$169.87	$169.85	$169.90
Purchase #6	$172.98	3.840%	$179.6224	$179.62	$179.60	$179.60
Purchase #7	$96.80	6.395%	$102.9904	$102.99	$103.00	$103.00
7 purchase totals =	$1,082.00		$1,164.3374	$1,164.34	$1,164.30	$1,164.20