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	$129.61	9.516%	$141.9437	$141.94	$141.95	$141.90
Purchase #2	$222.96	13.701%	$253.5077	$253.51	$253.50	$253.50
Purchase #3	$199.84	11.530%	$222.8816	$222.88	$222.90	$222.90
Purchase #4	$125.65	6.657%	$134.0145	$134.01	$134.00	$134.00
Purchase #5	$174.93	12.492%	$196.7823	$196.78	$196.80	$196.80
Purchase #6	$102.77	8.159%	$111.155	$111.16	$111.15	$111.20
Purchase #7	$59.85	5.242%	$62.9873	$62.99	$63.00	$63.00
7 purchase totals =	$1,015.61		$1,123.2721	$1,123.27	$1,123.30	$1,123.30