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	$117.29	8.743%	$127.5447	$127.54	$127.55	$127.50
Purchase #2	$132.46	11.334%	$147.473	$147.47	$147.45	$147.50
Purchase #3	$109.88	13.443%	$124.6512	$124.65	$124.65	$124.70
Purchase #4	$128.25	10.614%	$141.8625	$141.86	$141.85	$141.90
Purchase #5	$82.41	6.530%	$87.7914	$87.79	$87.80	$87.80
Purchase #6	$126.37	13.166%	$143.0079	$143.01	$143.00	$143.00
Purchase #7	$91.75	10.407%	$101.2984	$101.30	$101.30	$101.30
7 purchase totals =	$788.41		$873.6291	$873.62	$873.60	$873.70