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	$114.52	4.429%	$119.5921	$119.59	$119.60	$119.60
Purchase #2	$156.28	3.229%	$161.3263	$161.33	$161.35	$161.30
Purchase #3	$150.70	6.336%	$160.2484	$160.25	$160.25	$160.20
Purchase #4	$75.54	13.181%	$85.4969	$85.50	$85.50	$85.50
Purchase #5	$39.73	6.449%	$42.2922	$42.29	$42.30	$42.30
Purchase #6	$208.46	9.542%	$228.3513	$228.35	$228.35	$228.40
Purchase #7	$102.56	11.197%	$114.0436	$114.04	$114.05	$114.00
7 purchase totals =	$847.79		$911.3508	$911.35	$911.40	$911.30