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	$152.70	7.780%	$164.5801	$164.58	$164.60	$164.60
Purchase #2	$151.32	9.472%	$165.653	$165.65	$165.65	$165.70
Purchase #3	$62.79	3.584%	$65.0404	$65.04	$65.05	$65.00
Purchase #4	$91.30	11.291%	$101.6087	$101.61	$101.60	$101.60
Purchase #5	$221.47	5.435%	$233.5069	$233.51	$233.50	$233.50
Purchase #6	$141.55	11.498%	$157.8254	$157.83	$157.85	$157.80
Purchase #7	$127.61	10.207%	$140.6352	$140.64	$140.65	$140.60
7 purchase totals =	$948.74		$1,028.8497	$1,028.86	$1,028.90	$1,028.80