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	$66.94	12.469%	$75.2867	$75.29	$75.30	$75.30
Purchase #2	$117.84	10.531%	$130.2497	$130.25	$130.25	$130.20
Purchase #3	$178.96	8.738%	$194.5975	$194.60	$194.60	$194.60
Purchase #4	$200.79	10.817%	$222.5095	$222.51	$222.50	$222.50
Purchase #5	$208.50	8.136%	$225.4636	$225.46	$225.45	$225.50
Purchase #6	$123.41	5.587%	$130.3049	$130.30	$130.30	$130.30
Purchase #7	$167.63	9.681%	$183.8583	$183.86	$183.85	$183.90
7 purchase totals =	$1,064.07		$1,162.2702	$1,162.27	$1,162.25	$1,162.30