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	$244.71	9.546%	$268.07	$268.07	$268.05	$268.10
Purchase #2	$39.81	6.724%	$42.4868	$42.49	$42.50	$42.50
Purchase #3	$151.92	4.413%	$158.6242	$158.62	$158.60	$158.60
Purchase #4	$79.99	4.782%	$83.8151	$83.82	$83.80	$83.80
Purchase #5	$64.96	13.325%	$73.6159	$73.62	$73.60	$73.60
Purchase #6	$191.97	7.585%	$206.5309	$206.53	$206.55	$206.50
Purchase #7	$162.80	5.843%	$172.3124	$172.31	$172.30	$172.30
7 purchase totals =	$936.16		$1,005.4553	$1,005.46	$1,005.40	$1,005.40