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	$91.28	7.520%	$98.1443	$98.14	$98.15	$98.10
Purchase #2	$87.51	13.528%	$99.3484	$99.35	$99.35	$99.30
Purchase #3	$132.78	13.694%	$150.9629	$150.96	$150.95	$151.00
Purchase #4	$51.52	7.273%	$55.267	$55.27	$55.25	$55.30
Purchase #5	$178.79	5.792%	$189.1455	$189.15	$189.15	$189.10
Purchase #6	$45.83	7.428%	$49.2343	$49.23	$49.25	$49.20
Purchase #7	$214.25	8.471%	$232.3991	$232.40	$232.40	$232.40
7 purchase totals =	$801.96		$874.5015	$874.50	$874.50	$874.40