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	$153.25	11.419%	$170.7496	$170.75	$170.75	$170.70
Purchase #2	$19.90	5.280%	$20.9507	$20.95	$20.95	$21.00
Purchase #3	$158.57	4.108%	$165.0841	$165.08	$165.10	$165.10
Purchase #4	$60.82	10.334%	$67.1051	$67.11	$67.10	$67.10
Purchase #5	$130.29	5.779%	$137.8195	$137.82	$137.80	$137.80
Purchase #6	$77.94	7.245%	$83.5868	$83.59	$83.60	$83.60
Purchase #7	$100.84	11.431%	$112.367	$112.37	$112.35	$112.40
7 purchase totals =	$701.61		$757.6628	$757.67	$757.65	$757.70