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	$184.75	11.736%	$206.4323	$206.43	$206.45	$206.40
Purchase #2	$130.42	10.775%	$144.4728	$144.47	$144.45	$144.50
Purchase #3	$236.87	11.211%	$263.4255	$263.43	$263.45	$263.40
Purchase #4	$119.70	3.206%	$123.5376	$123.54	$123.55	$123.50
Purchase #5	$81.30	11.780%	$90.8771	$90.88	$90.90	$90.90
Purchase #6	$187.33	9.474%	$205.0776	$205.08	$205.10	$205.10
Purchase #7	$7.77	11.815%	$8.688	$8.69	$8.70	$8.70
7 purchase totals =	$948.14		$1,042.5109	$1,042.52	$1,042.60	$1,042.50