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	$91.94	6.849%	$98.237	$98.24	$98.25	$98.20
Purchase #2	$66.58	5.178%	$70.0275	$70.03	$70.05	$70.00
Purchase #3	$87.65	4.268%	$91.3909	$91.39	$91.40	$91.40
Purchase #4	$155.58	11.578%	$173.5931	$173.59	$173.60	$173.60
Purchase #5	$168.83	7.851%	$182.0848	$182.08	$182.10	$182.10
Purchase #6	$86.97	3.196%	$89.7496	$89.75	$89.75	$89.70
Purchase #7	$53.87	9.645%	$59.0658	$59.07	$59.05	$59.10
7 purchase totals =	$711.42		$764.1487	$764.15	$764.20	$764.10