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	$222.31	4.159%	$231.5559	$231.56	$231.55	$231.60
Purchase #2	$174.28	7.669%	$187.6455	$187.65	$187.65	$187.60
Purchase #3	$172.77	13.509%	$196.1095	$196.11	$196.10	$196.10
Purchase #4	$76.56	11.807%	$85.5994	$85.60	$85.60	$85.60
Purchase #5	$140.85	8.579%	$152.9335	$152.93	$152.95	$152.90
Purchase #6	$179.59	5.788%	$189.9847	$189.98	$190.00	$190.00
Purchase #7	$179.66	9.824%	$197.3098	$197.31	$197.30	$197.30
7 purchase totals =	$1,146.02		$1,241.1383	$1,241.14	$1,241.15	$1,241.10