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	$188.41	4.380%	$196.6624	$196.66	$196.65	$196.70
Purchase #2	$200.45	12.765%	$226.0374	$226.04	$226.05	$226.00
Purchase #3	$84.76	12.252%	$95.1448	$95.14	$95.15	$95.10
Purchase #4	$115.25	3.452%	$119.2284	$119.23	$119.25	$119.20
Purchase #5	$234.28	10.833%	$259.6596	$259.66	$259.65	$259.70
Purchase #6	$62.91	12.238%	$70.6089	$70.61	$70.60	$70.60
Purchase #7	$44.90	10.517%	$49.6221	$49.62	$49.60	$49.60
7 purchase totals =	$930.96		$1,016.9636	$1,016.96	$1,016.95	$1,016.90