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	$172.74	10.841%	$191.4667	$191.47	$191.45	$191.50
Purchase #2	$163.56	9.137%	$178.5045	$178.50	$178.50	$178.50
Purchase #3	$120.92	9.422%	$132.3131	$132.31	$132.30	$132.30
Purchase #4	$34.33	13.165%	$38.8495	$38.85	$38.85	$38.80
Purchase #5	$237.72	13.338%	$269.4271	$269.43	$269.45	$269.40
Purchase #6	$175.41	8.331%	$190.0234	$190.02	$190.00	$190.00
Purchase #7	$63.40	5.606%	$66.9542	$66.95	$66.95	$67.00
7 purchase totals =	$968.08		$1,067.5385	$1,067.53	$1,067.50	$1,067.50