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	$80.93	8.714%	$87.9822	$87.98	$88.00	$88.00
Purchase #2	$42.57	5.802%	$45.0399	$45.04	$45.05	$45.00
Purchase #3	$222.48	11.652%	$248.4034	$248.40	$248.40	$248.40
Purchase #4	$105.26	6.581%	$112.1872	$112.19	$112.20	$112.20
Purchase #5	$208.38	6.814%	$222.579	$222.58	$222.60	$222.60
Purchase #6	$137.50	12.317%	$154.4359	$154.44	$154.45	$154.40
Purchase #7	$136.80	10.249%	$150.8206	$150.82	$150.80	$150.80
7 purchase totals =	$933.92		$1,021.4482	$1,021.45	$1,021.50	$1,021.40