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	$77.88	6.299%	$82.7857	$82.79	$82.80	$82.80
Purchase #2	$155.31	3.206%	$160.2892	$160.29	$160.30	$160.30
Purchase #3	$125.81	3.384%	$130.0674	$130.07	$130.05	$130.10
Purchase #4	$158.44	4.698%	$165.8835	$165.88	$165.90	$165.90
Purchase #5	$142.69	9.691%	$156.5181	$156.52	$156.50	$156.50
Purchase #6	$212.86	6.763%	$227.2557	$227.26	$227.25	$227.30
Purchase #7	$215.53	11.272%	$239.8245	$239.82	$239.80	$239.80
7 purchase totals =	$1,088.52		$1,162.6241	$1,162.63	$1,162.60	$1,162.70