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	$174.77	8.179%	$189.0644	$189.06	$189.05	$189.10
Purchase #2	$18.54	4.741%	$19.419	$19.42	$19.40	$19.40
Purchase #3	$101.32	3.468%	$104.8338	$104.83	$104.85	$104.80
Purchase #4	$150.48	10.238%	$165.8861	$165.89	$165.90	$165.90
Purchase #5	$247.30	10.313%	$272.804	$272.80	$272.80	$272.80
Purchase #6	$24.86	11.491%	$27.7167	$27.72	$27.70	$27.70
Purchase #7	$177.62	7.187%	$190.3855	$190.39	$190.40	$190.40
7 purchase totals =	$894.89		$970.1095	$970.11	$970.10	$970.10