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	$111.67	10.643%	$123.555	$123.56	$123.55	$123.60
Purchase #2	$23.88	12.367%	$26.8332	$26.83	$26.85	$26.80
Purchase #3	$111.40	3.263%	$115.035	$115.04	$115.05	$115.00
Purchase #4	$188.68	6.272%	$200.514	$200.51	$200.50	$200.50
Purchase #5	$242.46	9.244%	$264.873	$264.87	$264.85	$264.90
Purchase #6	$57.63	3.831%	$59.8378	$59.84	$59.85	$59.80
Purchase #7	$97.41	6.528%	$103.7689	$103.77	$103.75	$103.80
7 purchase totals =	$833.13		$894.4169	$894.42	$894.40	$894.40