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	$239.58	13.367%	$271.6047	$271.60	$271.60	$271.60
Purchase #2	$10.61	11.514%	$11.8316	$11.83	$11.85	$11.80
Purchase #3	$38.77	12.197%	$43.4988	$43.50	$43.50	$43.50
Purchase #4	$146.93	12.167%	$164.807	$164.81	$164.80	$164.80
Purchase #5	$193.46	7.632%	$208.2249	$208.22	$208.20	$208.20
Purchase #6	$54.92	7.618%	$59.1038	$59.10	$59.10	$59.10
Purchase #7	$152.45	8.851%	$165.9433	$165.94	$165.95	$165.90
7 purchase totals =	$836.72		$925.0141	$925.00	$925.00	$924.90