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	$91.56	3.201%	$94.4908	$94.49	$94.50	$94.50
Purchase #2	$87.85	5.407%	$92.6	$92.60	$92.60	$92.60
Purchase #3	$72.43	13.402%	$82.1371	$82.14	$82.15	$82.10
Purchase #4	$48.35	10.747%	$53.5462	$53.55	$53.55	$53.50
Purchase #5	$223.35	9.526%	$244.6263	$244.63	$244.65	$244.60
Purchase #6	$127.26	12.421%	$143.067	$143.07	$143.05	$143.10
Purchase #7	$47.43	5.580%	$50.0766	$50.08	$50.10	$50.10
7 purchase totals =	$698.23		$760.5440	$760.56	$760.60	$760.50