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	$43.85	4.231%	$45.7053	$45.71	$45.70	$45.70
Purchase #2	$237.78	12.401%	$267.2671	$267.27	$267.25	$267.30
Purchase #3	$111.39	8.838%	$121.2346	$121.23	$121.25	$121.20
Purchase #4	$28.36	13.850%	$32.2879	$32.29	$32.30	$32.30
Purchase #5	$151.90	6.356%	$161.5548	$161.55	$161.55	$161.60
Purchase #6	$241.60	7.782%	$260.4013	$260.40	$260.40	$260.40
Purchase #7	$109.47	4.551%	$114.452	$114.45	$114.45	$114.50
7 purchase totals =	$924.35		$1,002.9030	$1,002.90	$1,002.90	$1,003.00