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	$77.71	11.223%	$86.4314	$86.43	$86.45	$86.40
Purchase #2	$173.46	3.271%	$179.1339	$179.13	$179.15	$179.10
Purchase #3	$91.55	13.197%	$103.6319	$103.63	$103.65	$103.60
Purchase #4	$45.89	3.329%	$47.4177	$47.42	$47.40	$47.40
Purchase #5	$239.80	8.801%	$260.9048	$260.90	$260.90	$260.90
Purchase #6	$192.88	3.779%	$200.1689	$200.17	$200.15	$200.20
Purchase #7	$193.61	6.865%	$206.9013	$206.90	$206.90	$206.90
7 purchase totals =	$1,014.90		$1,084.5899	$1,084.58	$1,084.60	$1,084.50