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	$62.63	4.107%	$65.2022	$65.20	$65.20	$65.20
Purchase #2	$135.39	3.667%	$140.3548	$140.35	$140.35	$140.40
Purchase #3	$65.78	7.147%	$70.4813	$70.48	$70.50	$70.50
Purchase #4	$134.60	7.670%	$144.9238	$144.92	$144.90	$144.90
Purchase #5	$185.59	8.134%	$200.6859	$200.69	$200.70	$200.70
Purchase #6	$30.45	4.623%	$31.8577	$31.86	$31.85	$31.90
Purchase #7	$138.41	5.194%	$145.599	$145.60	$145.60	$145.60
7 purchase totals =	$752.85		$799.1047	$799.10	$799.10	$799.20