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	$66.44	13.776%	$75.5928	$75.59	$75.60	$75.60
Purchase #2	$160.54	5.275%	$169.0085	$169.01	$169.00	$169.00
Purchase #3	$86.31	10.685%	$95.5322	$95.53	$95.55	$95.50
Purchase #4	$177.38	12.522%	$199.5915	$199.59	$199.60	$199.60
Purchase #5	$153.97	7.274%	$165.1698	$165.17	$165.15	$165.20
Purchase #6	$72.38	8.794%	$78.7451	$78.75	$78.75	$78.70
Purchase #7	$183.27	3.735%	$190.1151	$190.12	$190.10	$190.10
7 purchase totals =	$900.29		$973.7550	$973.76	$973.75	$973.70