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	$104.49	7.654%	$112.4877	$112.49	$112.50	$112.50
Purchase #2	$178.51	12.480%	$200.788	$200.79	$200.80	$200.80
Purchase #3	$209.44	10.701%	$231.8522	$231.85	$231.85	$231.90
Purchase #4	$6.56	10.705%	$7.2622	$7.26	$7.25	$7.30
Purchase #5	$196.42	4.631%	$205.5162	$205.52	$205.50	$205.50
Purchase #6	$39.60	9.361%	$43.307	$43.31	$43.30	$43.30
Purchase #7	$246.38	6.460%	$262.2961	$262.30	$262.30	$262.30
7 purchase totals =	$981.40		$1,063.5094	$1,063.52	$1,063.50	$1,063.60