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	$158.52	11.527%	$176.7926	$176.79	$176.80	$176.80
Purchase #2	$74.91	4.744%	$78.4637	$78.46	$78.45	$78.50
Purchase #3	$180.96	8.406%	$196.1715	$196.17	$196.15	$196.20
Purchase #4	$205.74	8.338%	$222.8946	$222.89	$222.90	$222.90
Purchase #5	$81.81	5.169%	$86.0388	$86.04	$86.05	$86.00
Purchase #6	$20.49	11.764%	$22.9004	$22.90	$22.90	$22.90
Purchase #7	$242.45	12.693%	$273.2242	$273.22	$273.20	$273.20
7 purchase totals =	$964.88		$1,056.4858	$1,056.47	$1,056.45	$1,056.50