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	$247.46	9.626%	$271.2805	$271.28	$271.30	$271.30
Purchase #2	$38.68	8.722%	$42.0537	$42.05	$42.05	$42.10
Purchase #3	$103.86	7.606%	$111.7596	$111.76	$111.75	$111.80
Purchase #4	$232.82	4.819%	$244.0396	$244.04	$244.05	$244.00
Purchase #5	$179.68	13.183%	$203.3672	$203.37	$203.35	$203.40
Purchase #6	$94.54	11.861%	$105.7534	$105.75	$105.75	$105.80
Purchase #7	$114.38	5.442%	$120.6046	$120.60	$120.60	$120.60
7 purchase totals =	$1,011.42		$1,098.8586	$1,098.85	$1,098.85	$1,099.00