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	$179.46	3.297%	$185.3768	$185.38	$185.40	$185.40
Purchase #2	$12.60	4.763%	$13.2001	$13.20	$13.20	$13.20
Purchase #3	$108.47	9.709%	$119.0014	$119.00	$119.00	$119.00
Purchase #4	$37.82	4.214%	$39.4137	$39.41	$39.40	$39.40
Purchase #5	$50.40	12.810%	$56.8562	$56.86	$56.85	$56.90
Purchase #6	$175.74	8.569%	$190.7992	$190.80	$190.80	$190.80
Purchase #7	$175.69	8.572%	$190.7501	$190.75	$190.75	$190.80
7 purchase totals =	$740.18		$795.3975	$795.40	$795.40	$795.50