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	$152.83	11.639%	$170.6179	$170.62	$170.60	$170.60
Purchase #2	$48.35	10.306%	$53.333	$53.33	$53.35	$53.30
Purchase #3	$226.34	11.341%	$252.0092	$252.01	$252.00	$252.00
Purchase #4	$37.92	4.405%	$39.5904	$39.59	$39.60	$39.60
Purchase #5	$196.78	7.781%	$212.0915	$212.09	$212.10	$212.10
Purchase #6	$196.52	8.550%	$213.3225	$213.32	$213.30	$213.30
Purchase #7	$36.53	3.462%	$37.7947	$37.79	$37.80	$37.80
7 purchase totals =	$895.27		$978.7592	$978.75	$978.75	$978.70