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	$199.72	10.389%	$220.4689	$220.47	$220.45	$220.50
Purchase #2	$41.51	12.304%	$46.6174	$46.62	$46.60	$46.60
Purchase #3	$150.99	9.562%	$165.4277	$165.43	$165.45	$165.40
Purchase #4	$126.64	11.513%	$141.2201	$141.22	$141.20	$141.20
Purchase #5	$95.60	8.183%	$103.4229	$103.42	$103.40	$103.40
Purchase #6	$182.25	3.362%	$188.3772	$188.38	$188.40	$188.40
Purchase #7	$168.33	3.811%	$174.7451	$174.75	$174.75	$174.70
7 purchase totals =	$965.04		$1,040.2793	$1,040.29	$1,040.25	$1,040.20