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	$117.60	7.862%	$126.8457	$126.85	$126.85	$126.80
Purchase #2	$107.35	7.274%	$115.1586	$115.16	$115.15	$115.20
Purchase #3	$106.82	12.227%	$119.8809	$119.88	$119.90	$119.90
Purchase #4	$52.56	13.829%	$59.8285	$59.83	$59.85	$59.80
Purchase #5	$74.86	12.153%	$83.9577	$83.96	$83.95	$84.00
Purchase #6	$151.43	11.220%	$168.4204	$168.42	$168.40	$168.40
Purchase #7	$177.59	4.111%	$184.8907	$184.89	$184.90	$184.90
7 purchase totals =	$788.21		$858.9825	$858.99	$859.00	$859.00