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	$190.38	10.480%	$210.3318	$210.33	$210.35	$210.30
Purchase #2	$187.60	13.302%	$212.5546	$212.55	$212.55	$212.60
Purchase #3	$114.31	3.687%	$118.5246	$118.52	$118.50	$118.50
Purchase #4	$243.64	9.617%	$267.0709	$267.07	$267.05	$267.10
Purchase #5	$46.29	11.854%	$51.7772	$51.78	$51.80	$51.80
Purchase #6	$68.54	6.335%	$72.882	$72.88	$72.90	$72.90
Purchase #7	$199.88	12.730%	$225.3247	$225.32	$225.30	$225.30
7 purchase totals =	$1,050.64		$1,158.4658	$1,158.45	$1,158.45	$1,158.50