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	$235.55	9.488%	$257.899	$257.90	$257.90	$257.90
Purchase #2	$40.51	7.489%	$43.5438	$43.54	$43.55	$43.50
Purchase #3	$214.61	13.170%	$242.8741	$242.87	$242.85	$242.90
Purchase #4	$69.52	12.241%	$78.0299	$78.03	$78.05	$78.00
Purchase #5	$158.31	12.580%	$178.2254	$178.23	$178.25	$178.20
Purchase #6	$223.29	7.219%	$239.4093	$239.41	$239.40	$239.40
Purchase #7	$34.25	6.303%	$36.4088	$36.41	$36.40	$36.40
7 purchase totals =	$976.04		$1,076.3903	$1,076.39	$1,076.40	$1,076.30