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	$68.25	12.776%	$76.9696	$76.97	$76.95	$77.00
Purchase #2	$178.34	4.242%	$185.9052	$185.91	$185.90	$185.90
Purchase #3	$72.50	7.781%	$78.1412	$78.14	$78.15	$78.10
Purchase #4	$155.31	10.417%	$171.4886	$171.49	$171.50	$171.50
Purchase #5	$101.38	13.270%	$114.8331	$114.83	$114.85	$114.80
Purchase #6	$103.57	6.795%	$110.6076	$110.61	$110.60	$110.60
Purchase #7	$138.84	9.726%	$152.3436	$152.34	$152.35	$152.30
7 purchase totals =	$818.19		$890.2889	$890.29	$890.30	$890.20