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	$229.77	5.241%	$241.8122	$241.81	$241.80	$241.80
Purchase #2	$84.30	4.148%	$87.7968	$87.80	$87.80	$87.80
Purchase #3	$54.35	9.672%	$59.6067	$59.61	$59.60	$59.60
Purchase #4	$147.31	9.761%	$161.6889	$161.69	$161.70	$161.70
Purchase #5	$105.78	11.775%	$118.2356	$118.24	$118.25	$118.20
Purchase #6	$186.90	7.456%	$200.8353	$200.84	$200.85	$200.80
Purchase #7	$178.44	4.706%	$186.8374	$186.84	$186.85	$186.80
7 purchase totals =	$986.85		$1,056.8129	$1,056.83	$1,056.85	$1,056.70