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	$150.86	4.758%	$158.0379	$158.04	$158.05	$158.00
Purchase #2	$99.33	9.150%	$108.4187	$108.42	$108.40	$108.40
Purchase #3	$75.61	5.815%	$80.0067	$80.01	$80.00	$80.00
Purchase #4	$64.80	13.119%	$73.3011	$73.30	$73.30	$73.30
Purchase #5	$222.92	8.482%	$241.8281	$241.83	$241.85	$241.80
Purchase #6	$19.54	7.516%	$21.0086	$21.01	$21.00	$21.00
Purchase #7	$73.45	7.237%	$78.7656	$78.77	$78.75	$78.80
7 purchase totals =	$706.51		$761.3667	$761.38	$761.35	$761.30