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	$154.30	9.143%	$168.4076	$168.41	$168.40	$168.40
Purchase #2	$69.79	11.560%	$77.8577	$77.86	$77.85	$77.90
Purchase #3	$174.77	8.615%	$189.8264	$189.83	$189.85	$189.80
Purchase #4	$24.95	11.151%	$27.7322	$27.73	$27.75	$27.70
Purchase #5	$75.48	13.559%	$85.7143	$85.71	$85.70	$85.70
Purchase #6	$200.88	10.639%	$222.2516	$222.25	$222.25	$222.30
Purchase #7	$152.70	13.492%	$173.3023	$173.30	$173.30	$173.30
7 purchase totals =	$852.87		$945.0921	$945.09	$945.10	$945.10