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	$200.31	11.225%	$222.7948	$222.79	$222.80	$222.80
Purchase #2	$60.29	7.134%	$64.5911	$64.59	$64.60	$64.60
Purchase #3	$119.71	7.273%	$128.4165	$128.42	$128.40	$128.40
Purchase #4	$21.28	4.839%	$22.3097	$22.31	$22.30	$22.30
Purchase #5	$137.41	4.646%	$143.7941	$143.79	$143.80	$143.80
Purchase #6	$61.29	6.275%	$65.1359	$65.14	$65.15	$65.10
Purchase #7	$118.57	8.606%	$128.7741	$128.77	$128.75	$128.80
7 purchase totals =	$718.86		$775.8162	$775.81	$775.80	$775.80