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	$40.62	5.487%	$42.8488	$42.85	$42.85	$42.80
Purchase #2	$99.59	8.127%	$107.6837	$107.68	$107.70	$107.70
Purchase #3	$46.95	7.286%	$50.3708	$50.37	$50.35	$50.40
Purchase #4	$149.98	11.834%	$167.7286	$167.73	$167.75	$167.70
Purchase #5	$59.85	13.158%	$67.7251	$67.73	$67.75	$67.70
Purchase #6	$218.86	4.445%	$228.5883	$228.59	$228.60	$228.60
Purchase #7	$34.97	11.659%	$39.0472	$39.05	$39.05	$39.00
7 purchase totals =	$650.82		$703.9925	$704.00	$704.05	$703.90