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	$208.29	5.159%	$219.0357	$219.04	$219.05	$219.00
Purchase #2	$139.96	9.370%	$153.0743	$153.07	$153.05	$153.10
Purchase #3	$171.69	11.357%	$191.1888	$191.19	$191.20	$191.20
Purchase #4	$63.56	4.514%	$66.4291	$66.43	$66.45	$66.40
Purchase #5	$37.60	4.322%	$39.2251	$39.23	$39.25	$39.20
Purchase #6	$211.96	12.577%	$238.6182	$238.62	$238.60	$238.60
Purchase #7	$90.32	10.590%	$99.8849	$99.88	$99.90	$99.90
7 purchase totals =	$923.38		$1,007.4561	$1,007.46	$1,007.50	$1,007.40