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	$170.81	11.374%	$190.2379	$190.24	$190.25	$190.20
Purchase #2	$137.25	12.265%	$154.0837	$154.08	$154.10	$154.10
Purchase #3	$171.40	6.576%	$182.6713	$182.67	$182.65	$182.70
Purchase #4	$92.45	7.390%	$99.2821	$99.28	$99.30	$99.30
Purchase #5	$76.65	7.761%	$82.5988	$82.60	$82.60	$82.60
Purchase #6	$65.33	12.383%	$73.4198	$73.42	$73.40	$73.40
Purchase #7	$148.94	6.623%	$158.8043	$158.80	$158.80	$158.80
7 purchase totals =	$862.83		$941.0979	$941.09	$941.10	$941.10