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	$208.58	10.148%	$229.7467	$229.75	$229.75	$229.70
Purchase #2	$243.87	11.290%	$271.4029	$271.40	$271.40	$271.40
Purchase #3	$53.56	4.803%	$56.1325	$56.13	$56.15	$56.10
Purchase #4	$68.94	12.235%	$77.3748	$77.37	$77.35	$77.40
Purchase #5	$156.64	11.509%	$174.6677	$174.67	$174.65	$174.70
Purchase #6	$188.45	4.322%	$196.5948	$196.59	$196.60	$196.60
Purchase #7	$106.30	10.721%	$117.6964	$117.70	$117.70	$117.70
7 purchase totals =	$1,026.34		$1,123.6158	$1,123.61	$1,123.60	$1,123.60