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	$198.40	4.168%	$206.6693	$206.67	$206.65	$206.70
Purchase #2	$177.96	7.108%	$190.6094	$190.61	$190.60	$190.60
Purchase #3	$225.25	3.452%	$233.0256	$233.03	$233.05	$233.00
Purchase #4	$92.52	9.412%	$101.228	$101.23	$101.25	$101.20
Purchase #5	$89.75	11.658%	$100.2131	$100.21	$100.20	$100.20
Purchase #6	$101.32	7.824%	$109.2473	$109.25	$109.25	$109.20
Purchase #7	$108.70	6.243%	$115.4861	$115.49	$115.50	$115.50
7 purchase totals =	$993.90		$1,056.4788	$1,056.49	$1,056.50	$1,056.40